Introduction

Zeolites can be found in varying quantities all along the southern side of the Bay of Fundy from Cape Split to Brier Island. This is known as the North Mountain. For collectors, probably the best stretch of coastline is from Harbourville to east of Halls Harbour. This area has a good concentration of minerals, although there are others. The best spots are where the top of a given lava flow dips low enough to be accessible at beach level. Stilbite and heulandite are nearly ubiquitous and laumontite is very common. Many other minerals occur is smaller amounts.

Roughly 10 km west of Harbourville lies the town of Morden, the type locality for mordenite. This shoreline is also where okenite and gyrolite were first reported in Canada.

History

All along the Bay of Fundy the basalt cliffs, or trap as they used to be called, have been known to produce fine zeolites. The first reports were by Alger and Jackson in the late 1820s. After hearing about those trips, Emmons and Hopkins arranged a geology trip from Williams College in Boston in 1835. They stopped at Peter's Point (just east of Margaretsville, halfway to Morden) and spots near Digby, among other locations (Hopkins 1835, Emmons 1836). They described excitedly collecting stilbite and laumontite. There is also a list from the early 1800s that was published in the late 1800s (McCulloch 1892).

In the 1860s How (for whom howlite is named) went over the area in detail with a scientific eye. He published a few papers on his work in the area (How 1858, etc). To the west of Harbourville he discovered gyrolite (How 1861). Between Margaretsville and Harbourville, he described a new zeolite, which would eventually be named mordenite in honor of the nearest town in the area (How 1863).

Economic development of the North Mountain has for the most part been limited to small quarries. However in the 1800s there was some minor development of iron and copper. The community of Margaretsville lies about 20 km west of Harbourville. At Margaretsville small amounts of copper minerals can be found. In the old literature, this town is called Margaretville, without the 's'; the name was changed in the mid 1900s and some buildings in the town still bear the original spelling. Hamilton (1865) writes

The Mine of the Annapolis Copper Company, is situate near Margaretville, Wilmont, in the County of Annapolis. It is now worked by a Company from the Northern States, of which Mr. George L. Dix is President and Manager. During the past year $2,500 have been expended in sinking a pit, erecting pump, derricks, &c. The works at this place are not sufficiently advanced to enable me to express any opinion as to the prospects of the mine; but the licensees appear to be sanguine as to the eventual success of their enterprise.

and How (1869) writes,

The most productive locality has been thought to be Margaretville or Peter's Point. I saw it in this neighbourhood 12 years ago. In 1862 a company, formed in Halifax, prospected here and commenced operations at Bishop's Brook some 2 or 3 miles east of the Village. The metal was found crystallized in a matrix of zeolite running through the trap, and appeared to be most abundant in the rock on the beach exposed at half tide. A considerable excavation was made and about three hundred weight of metal got out during the summer. I visited the spot the next summer and found the place abandoned. The metal occurs close to the wharf at Margaretvile in zeolite in the trap and also in rocks exposed at half-tide, as well as near a brook a few yards to the east and again about 1 1/2 mile back from the shore. An American company has been working at this last locality; in 1864 $2500 were expended in operations: the licensees appeared sanguine as to their eventual success. Operations however have been abandoned.

Iron ore, in the form of magnetite and hematite was worked at several places in the Digby area. Baily (1896) writes,

Iron ores are both the most abundant and most interesting of these minerals. They occupy veins traversing the trappean rock, and with a tendency, apparently, to run north and south directions. They occur at many points, the most prominent being along the road from Digby to Digby Light, Nicholl's mine in Rossway, Johnson's Mine in Waterford, and Morehouse's mine on the St. Mary's Bay shore near Sandy Cove. At several of these points attempts have been made to remove the ore, and considerable money has been spent, but the small size of the veins and the cost of removal have in all instances prevented them from being remunerative....The mining never proceeded beyond the digging of shallow trenches in the side of the hills, and these are now largely filled with rubbish.

Additional prospecting was carried out in the early 1900s by the Dominion Iron and Steel Company, south of Rossway at Waterford and Centreville (Wright 1975).

In the late 1990s, C2C Zeolite Corporation performed some mapping and drilling for a potential zeolite mine north of Berwick. In 2001 they received conditional environmental approval, but to my knowledge no further work was done. Zeolites are very beneficial; their chemical structure allows them to be used as molecular sieves. Diverse uses include additives to animal feed, water softeners, and cat litter. While some zeolites can be produced artificially, mining areas of highly concentrated natural zeolites can be less expensive.

Geology

The North Mountain basalt is an immense lava flow sequence that covers most of the Fundy basin. It was formed roughly at the Triassic-Jurassic boundary. It overlies the Triassic age Blomidon Formation (sandstone) and just east of Ross Creek, it is overlain by the Early Jurassic age McCoy Brook Formation. It is part of a gigantic intrusive complex of the same age (200 Ma), stretching from northern South America to Europe.

In general, the basalt is gray and hard but it can range from vesicular and mineral rich to columnar and mineral poor. Distinct lava flows are visible in the cliffs from the beach at many locations. While molten, gas bubbles migrated to the tops of these flows and were later lined with the various zeolites. The number of bubbles can be quite large, making the basalt crumbly at times, although larger bubbles that produce good specimens are more difficult to find. This mineralized basalt at the top of a flow erodes more quickly than the bottom of the flow above it, resulting in undercuts, as shown below.

Tubular amygdaloid, in otherwise uniform basalt, is also sometimes seen in this area. They formed as vapours rose vertically through the molten lava. As the rock cooled, the bubbles were frozen in place that later filled with zeolites. Walker and Parsons (1923) suggest that the vapours derive from heating of the moist underlying rocks, rather than the new lava. They also write,

The most spectacular development of tubular amygdaloid yet observed was found in the central cliff at Ste. Croix Cove, where the amygdaloidal tubes reach a maximum of six inches in diameter. They extend from the amygdaloidal basal portion of the flow, through the more compact central part to the porous upper portion.

The two photos below show an interesting structure located a short distance east of Halls Harbour. It is a very large and semicircular in cross section. On closer inspection, there are a serial of large pockets that extend radially wihin the structure. It is quite interesting and possibly unique in the area. It seems to be the horizontal limit of that particular lava flow that formed fractures as it cooled and settled into place.

Mineralogy

The most abundant minerals along this stretch of shoreline are heulandite, stilbite, and laumontite. Other minerals include analcime, apophyllite, calcite, chabazite, hematite, mesolite, and quartz. Celadonite, a green mica mineral with no macroscopic structure, is often found as a thin layer on the outside of zeolite pockets. A bit further from Harbourville, mordenite, thomsonite, gyrolite, magnetite, and native copper have been found. Associated with the copper are secondary minerals cuprite and chrysocolla (and presumably malachite as a weathering product). Barite is reported by How (1863) and Pe-Piper (2000). Okenite was reported by Walker and Parsons (1922). Epistilbite is reported by Bray (1986) and Pe-Piper (2000). Galena is mentioned in passing by Bailey (1896).

Bray also reports chlorite, chlorophaeite, and pumpellyite. Both chlorite and pumpellyite are mineral groups. Bray warns that the chlorite identification is uncertain. Chlorophaeite is an approved but questionable species. Bray's description suggests the material is what other authors have called celadonite. Pe-Piper mentions smectite and at least three different Mg–Fe–Na aluminosilicates. Due to the difficulty in analyzing these minerals, these three species have not been listed below.

Gilpin (1881) reports stibnite from Margaretsville and prehnite from Black Rock. The stibnite is almost surely in error and I have not seen any substantiation for prehnite. Gilpin's listing might be from How (1863) who describes, from Morden, something that looked like prehnite but the chemistry was wrong. I will not consider it any further.

Table 1: Minerals reported from the North Mountain basalt.

Analcime - NaAl(Si₂O₆)·(H₂O)

Analcime is uncommon in this area and I'm not aware of any significant specimens. Walker and Parsons (1922) note that they did not find any analcime west of Stronach's Brook, roughly the line between Kings and Annapolis Counties. Opaque white crystals to over 3 cm have been found, but most are much smaller. The color for most crystals is white, but orange and even deep red-brown specimens have been found. Jackson and Alger (1829) reported verdigris green to emerald green crystals at Martial's Cove (now Marshall Cove / Port Lorne), due to included copper and copper secondary minerals. In 2021, I found a couple crystals, associated with thomsonite and mesolite, with a silky luster. Under magnification they are seen be be partly replaced by mesolite. This replacement has also been observed (more completely) are Cape D'Or.

Barite - BaSO₄

How (1863) reported barite is filling the center of a modenite nodule at Morden. Pe-Piper (2000) also reported barite as microscopic rosettes. At first barite seems an unusual mineral for the basalts, but it has been found in small amounts at other localities including Five Islands and Swan Creek. At this locality it does not form macroscopic crystals. Unfortunately, barite-bearing zeolites (ex. brewsterite, edingtonite, harmotome) have not been reported from Nova Scotia yet, but it might be worth looking.

Calcite - CaCO₃

On occasion, small calcite crystals can be found on top of the zeolites. In general, calcite here is far less common than on the north side of the Bay of Fundy. The few crystals that I have seen tend to be blocky, dominated by a rhombohedral form.

The color tends to be white to pale yellow, and they typically fluoresce and phosphoresce green. Measurement with a spectrometer (shown below) shows a broad peak centered at about 490 nm, which is near blue, but our eyes are more sensitive to green. The small sharp peak at 435 nm is an artifact of the measurement system. Most sources say that green (visually) fluorescence in calcite is usually caused by organic molecules and less commonly by uranium. The activator in this case is unknown, however, an organic source seems unlikely and fluorecent gmelinite from Amethyst Cove shows a clear signature of uranium.

Celadonite - K(Mg,Fe²⁺)(Fe³⁺,Al)(Si₄O₁₀)(OH)₂

Celadonite (not to be confused with the mineral caledonite), is a member of the muscovite mica group of minerals. It was usually the first mineral to form in the amygdules. Sometimes when a relatively smoothly shaped pocket is found, the minerals will easily separate from the basalt matrix due to the poor adhesion of the celadonite. In these cases the celadonite can be seen as a green coating on the outside of the pocket. No crystals are found.

Chabazite-Ca - CaAl₂Si₄O₁₂·6(H₂O)

Jackson and Alger (1829) describe chabazite crystals to more than 2 cm, on quartz, from Mink Cove and also from Sandy Cove.

Further east, Bray (1986) reports it from Croskill Lake, Viewmont, and Garland, which are all inland localities. Despite these reports, I have not heard of it reported from the shoreline between Ross Creek and Margaretsville where most collectors are likely to visit. Those inland localities may represent different lava flows with different mineralization. I've selected the -Ca species of chabazite here because it is the most common type of chabazite, but I have not seen any chemical analyses.

In 2020 Rod Tyson carried out a project at Glenmont, also inland, and found some very large white crystals. I obtained one specimen with a partial crystal that is 4 cm diagonal on a face. It is associated with thomsonite, heulandite, and analcime - an assemblage I have not seen elsewhere around the Fundy.

Chrysocolla - Cu_2-xAl_x(H_2-xSi₂O₅)(OH)₄·nH₂O, (x < 1)

Some attractive blue-green chrysocolla has been found coating heulandite and analcime. It forms glassy botryoidal or rounded globules that form bubbly crusts or random structures entirely of chrysocolla. The mineral is associated with native copper.

Copper - Cu

Native copper has been found in the vicinity of Margaretsville. In the 1860s it was worked on a very small scale at two locations (see history section). A couple small but nicely crystallized specimens of native copper from the Margaretsville area (likely the workings described above) reside in the Nova Scotia Museum of Natural History collection. Surprisingly, a specimen from this area was even displayed at the Antwerp Universal Exhibition in 1885, as part of the collection of J. Grant of Halifax (item 73) [Antrewp Universal Exhibition 1885]. The only native copper that I've found forms tiny massive blebs altering to cuprite and chrysocolla. These were found just east of the wharf at Margaretsville, below the church.

Copper has also been reported in small amounts from the Digby area.

Epistilbite - CaAl₂Si₆O₁₆·5(H₂O)

Epistilbite was reported by How (1858) but he later doubted the identification, thinking instead it was heulandite (Marsh 1863). Bray (1986) reported epistilbite from several localities including Brown Mountain Road, Viewmont, Garland, Grafton, Pelton Mountain, Glenmont, and North Arlington Road, using X-ray diffraction and thin section. Epistilbite was identified by Pe-Piper (2000) from Ross Creek. It would appear that these reports are all by slicing samples; I am not aware of any free standing crystals of any size.

The specimen figured below is the sample Z650 from Pe-Piper (2000). It is a small amygdale that was sliced, revealing three very distinct zones; an outer zone of mordenite and an inner zone of epistilbite, separated by a dark zone with Fe–Mg–Na aluminosilicates and mordenite. In the paper, the X-ray results are presented in Figure 6B, however it appears that 'Zone 3 mordenite' should read 'Zone 3 epistilbite'. Below, I've shown the XRD results for the epstilbite from that paper, in black, and compared them to XRD data for epistilbite from Iceland, collected by RRUFF (red, https://rruff.info/Epistilbite), and simulated data from the International Zeolite Association (Treacy and Higgins, 2001). It is clear that there is a good correlation between the peaks of the three data sets. The data sets are aligned by angle, but the vertical scale is somewhat arbitrary and the curves are offset to make them more visible.

Fluorapatite - Ca₅(PO₄)₃F

Apatite crystals have been reported (George O'Reilly, personal communication, Aug 2018) associated with magnetite and amethyst at Slokum Brook. The apatite was identified by energy dispersive SEM. I'm making the assumption it was fluorapatite as that is by far the most common type of apatite. It is interesting that Horner (1939) reported apatite with magnetite at Economy (Gerrish) Mountain.

Fluorapophyllite-(K) - KCa₄(Si₄O₁₀)₂F·8(H₂O)

Apophyllite can be found in some of the pockets and veins. It forms blocky crystals, generally below a centimeter. The color varies from colorless to a pale green and rarely the desirable intense green. To the west of Harbourville, in the Margaretsville area, apophyllite becomes more abundant and reportedly can sometimes be embedded with gyrolite. I am unaware of any great specimens collected from this area of the Bay of Fundy recently, but in the past it was the source of great specimens. The one shown below was collected in the 1960's or 1970's by the late Harry Crossman. Another specimen from the find can be found in the Canadian Museum of Nature on display (2013 - pers. comm. Michel Picard). It is 20 cm in length with several apophyllite crystals to 5 cm! I have a specimen collected more recently with partial white crystals that reach 5.5 cm on an edge.

Apophyllite is now a group name for three species, which have been renamed as of 2013 (Hatert et al). They are fluorapophyllite-(K), fluorapophyllite-(Na), and hydroxyapophyllite-(K). The first is in general by far the most common. At Morden, both fluorapophyllite-(K) and fluorapophyllite-(Na) have been identified (Pe-Piper 2000).

Goethite - Fe³⁺O(OH)

Some quartz specimens from Harbourville (see the quartz section on this page) shown yellow-brown root-like structures both within and outside of the quartz. A mineral with identical color and habit, in and outside of chabazite has been found at Cape D'Or and has been identified (EDS and Raman) as goethite. The Hall's Harbour material has not been tested but is undoubtedly the same. Goethite horsetails have been found included in amethystine quartz from Cape Split / Amethyst Cove and may also be present in Hall's Harbour amethyst, but I haven't seen any to date.

Gyrolite - Ca₄(Si₆O₁₅)(OH)₂·3H₂O

Gyrolite is a zeolite associate. It was first reported from this locality by How 1861. At the time it was a very rare mineral, having only been described only ten years earlier and known from only two localities. How states:

I met with it in Anapolis [sic] County, N. S., some 25 miles S. W. of Cape Blomidon, between Margaretville and Port George, on the surface of fractured crystalline apophyllite, and, on further breaking the mass a good many spherical concretions of pearly lustrous plates were observed in the interior, of sizes varying from that of a pin's head to nearly half-an-inch in diameter.

Some of the numerous cavities in the apophyllite were empty, some entirely filled with gyrolite, and in others separate plates of this mineral were standing edgewise, leaving vacant spaces, while upon and by the side of the plates were in some cases rhombohedral crystals which proved to consist of calcite and were sometimes present alone in the cavities, which varied from being quite shallow to half an inch in depth.

There is a specimen in the Yale mineral collection (catalog number YPM MIN 022658, Online) and another in the Canadian Museum of nature collection (CMNMC 40536). The latter was collected at Chipman Brook, near Hall's Harbour. As collected, it was a solid pocket with small gyrolites and otherwise filled with montmorillonite. On the broken surfaces the gyrolite forms small radial aggregates that are fairly nondescript. They could easily be overlooked; perhaps the mineral is more common than is reported.

The chemical analysis by How gave SiO2=51.90, Al2O3=1.27, MgO=0.08, CaO=29.95, K2O=1.60, H2O=15.05.

Hematite - Fe₂O₃

Iron is the impurity that makes give the heulandite its oranges and reds and quartz its amethystine color, but tends not to form minerals itself. Goethite is certainly possible, as so-called horsetail growths in amethyst. Amethyst was found at Hall's Harbour back in the 1970s(?) but I have not had a chance to examine any to look for goethite. I have however seen a single example of hematite, actually on the same specimen as the wheel of thomsonite shown below. It is microscopic, forming linear structures composed of tiny balls of hematite. These structures are included within the heulandite and also span between crystals.

Further down the shore, near Digby, were small iron working in the 1800s. They were working magnetite but there was hematite too. Jackson and Alger (1829) write,

"specular iron ore...affords specimens not inferior in beauty to those from Elba [Italy]. When not massive, it occurs in flat, tabular crystals, often with curvilinear and striated faces."

In 1844, Francis Alger writes about the same material (Phillips 1844),

"In Nova Scotia, specular iron ore forms veins in the trap rocks at several places along the shores of the Bay of Fundy, and is sometimes in crystals, which present portions of the planes of the primary rhomboid. The most beautiful specimens are from Sandy Cove, where it is associated with siliceous sinter and laumontite, and sometimes with agate and jasper."

In 1888, George Kunz wrote the passage below, but it isn't clear if he saw any material or was basing his description on the writings of others.

"Hematite (specular iron) occurs finely crystallized at Cape Spencer, and exceptionally perfect and brilliant at Digby Neck, NS."

Also reported from these deposits are hematite pseudomorphs after magnetite. These are often referred to as martite. Most of the specimens are quite old. I have some that were reportedly collected in the 1960s/70s but the locality is uncertain. Old specimens from the workings were well known and are in many museum collections in Canada and the United States.

Heulandite-Ca - (Ca,Na)₉Al₉Si₂₇O₇₂·24(H₂O) and
Heulandite-K - (K,Na)₉Al₉Si₂₇O₇₂·24(H₂O) and
Clinoptilolite-Ca - (Ca,Na)₆Al₆Si₃₀O₇₂·20(H₂O) and
Clinoptilolite-Na - (Na,Ca)₆Al₆Si₃₀O₇₂·20(H₂O)

Heulandite is probably the most common mineral in the area. It lines most of the numerous pockets and vugs in the basalt. Color ranges from a beautiful pink, to white, colorless, reddish, and bright orange. The crystals are typically small, less than one centimeter. Larger crystals are rare. Referring to the drawing below, most crystals display only the 101 and 010 forms and in druses only the top half of the crystal is seen. Thus they look like little chisel tips or wedges - not the coffin shape that many beginner collector guides say to look for when looking for heulandite. Heulandite is found both under on top of stilbite.

Aggregates of heulandite occasionally form rounded growths. To the east, at Hall's Harbour, these growths become botryoidal and can be mistaken for chalcedony at first glance. Those were first noticed by collector Terry Collett. Some micro-sized balls of heulandite are shown below from Bishops Mountain, collected from a block that fell from higher in the cliff. This stretch of beach is nearly devoid of other mineralization. These have not been analyed to see if there might be a chemical difference that might cause this habit. These balls and especially the botryoidal material are a very unusual habit for heulandite. A ball-like habit sometimes indicates a high Si/Al ratio (i.e. clinoptilolite) (pers. comm. Volker Betz 2020) and there are other indications of high silica zeolites in the general area (ex. mordenite) so that is a very plausible identity.

And now for some chemistry. The difference between heulandite and clinoptilolite is in the ratio of Si/Al. These two minerals are the only zeolites to be given separate identities based on this ratio, and it was defined this way only because the two names were already widely used. In heulandite Si/Al < 4.0 and in clinoptilolite Si/Al >= 4.0; a continuous series is formed between the two. Visually they are indistinguishable.

In addition, both heulandite and clinoptilolite are assigned individual species names based on the dominant ion. For heulandite it may be Ca, Na, K, Ba, or Sr. For clinoptilolite it may be Ca, Na, or K (Ba or Sr dominant examples are so far unknown). Along the North Mountain clinoptilolite has been reported from the Arlington Quarry, identified through microprobe analysis (Pe-Piper). Pe-Piper reports both clinoptilolite-Ca and a single sample of clinoptilolite-Na from Morden, and both heulandite-Ca and a single sample of heulandite-K, also from Morden.

Laumontite - CaAl₂Si₄O₁₂·4(H₂O)

Laumontite is very common and can be quite attractive when fresh. A newly exposed pocket can reveal large surfaces of colorless crystals. Unfortunately, when this mineral is exposed to the air it begins to lose water, turning into a crumbly white powder. Specimens can be preserved by placing them in an airtight jar with some water to maintain a high humidity.

Crystals may be isolated and are often doubly terminated, when growing on another mineral such as stilbite. More commonly the crystals form aggregates. The aggregates may be coarsely spiked, resembling the Sydney Opera House. The example below is quite unusual in that the aggregate has nearly formed a sphere. The deep orange color is also atypical.

Below is an idealized drawing of a laumontite crystal from Margaretsville, by Walker and Parsons (1922). The forms include m (110), e (-101), c (001) and what they describe as a new pyramid, possibly (12.1.11) indicated by q. The prismatic habit gives an indication of the temperature of formation (Kostov 1967, Ghobarkar and Schäf 1998). At low temperatures (30°C) laumontite crystals are very slender, at temperatures of 250-300°C crystals are fairly equant, and at high temperatures of 450°C, crystals are platy. Based of this information, we might estimate that most North Mountain laumontite formed around 100-150°C.

Even with the tremendous amount of laumontite in the North Mountain, no twinned laumontite crystals are reported in the historical literature. In 2021, Terry Collett found a pocket with many "swallow tail" twins, which are twinned on {100} and produce notches at the end of the crystals. They were transparent when collected. Tschernich (1992) writes that such twins are common, but based on photos submitted to Mindat.org, they do not seem to be, with the exception of the Bishop Mining District in California which is a classic laumontite locality with huge crystals that are nearly always twinned. Perhaps that contributed to their large size.

Magnetite-Magnesioferrite - Fe³⁺₂Fe²⁺O₄ - MgFe³⁺₂O₄

Several locations in Kings and Annapolis Counties have produced small amounts of magnetite, but these are inland - I am not aware of any on the shore. One, in a pasture in Grafton was prospected in 1941 and produced a few truck loads of ore (Wright 1975). Hornor analysed some material from Lakeville, King's County and found that it contained some magnesium. He suggested that it best be described as a member of the magnetite-magnesioferrite series. He also describes that the color is deep black with a pitch-like luster which helps to distinguish it from bluish-gray pure magnetite.

The most widely reported magnetite from the North Mountain was from the Digby area where is was found and prospected at several locations (see history section). The magnetite was found in irregular veins and sometimes associated with amethyst making attractive combinations (Bailey 1896). Jackson and Alger (1829) describe some loose, weathered out crystals as,

...large and very perfect crystals, in the form of the primary octahedron, exhibiting passage of this form into rhombic dodecahedrons, which they sometimes complete...

Malachite - Cu₂(CO₃)(OH)₂

In general malachite can be expected in small amounts when copper is present. I found a rounded beach rock east of Margaretsville in 2021 with a small amount of earthy malachite and a small mound of proper crystals. The malachite is associated with some cuprite and a black submetallic mineral that it looks like a copper sulfide. There are also bright malachite crystals in tiny pockets inside the rock, but too tiny for me to photograph. The rock could have been glacially transported to that location, but given that copper is already known from the area, it is also reasonable that it was local.

Mesolite - Na₂Ca₂Al₆Si₉O₃₀·8(H₂O)

Mesolite is uncommon in this area and I'm not aware of any good specimens. Walker and Parsons (1922) report that they examined specimens from around Margaretsville and Port Lorne that visually appeared to be natrolite but all of them tested to be mesolite - suggesting that all earlier reports of natrolite along this shore (none of which were supported with analyses) were actually mesolite. That makes them the coarsest mesolites along the Bay of Fundy, as the material from Cape D'Or is extremely fine and hairlike. Walker and Parsons found mesolite at Chute Cove, Port George, Stronach Brook, and the shore opposite Gates Mountain and posit that natrolite is not found west of a line from Cape D'Or to Cape Split (i.e. the entire area covered by this page).

According the Kostov (1967), mesolite (and natrolite) crystals have a larger length-to-width ratio when they form at lower temperatures, and are more stout and robust when they form at higher temperatures. The relatively coarse mesolite that I've seen from the North Mountain has formed in pockets, consistent with higher temperature (i.e. the new rock was still warm when mineralization occurred), while the hairlike mesolite from Cape D'Or forms in fault veins and breccias that formed after the rock was cooled. This is consistent with Kostov's work.

Mesolite from Peter's Point was used in a thermal study of mesolite, natrolite, and scolecite (Peng 1955), as was a mesolite from Cape D'Or. The Peter's Point material is described as 'divergent groups of white slender needles'. Walker and Parsons (1922) describe radiating specimens from the western side of Digby Gut with the inner portion being mesolite and the outer part being scolecite.

Mesolite contains both sodium and calcium as essential elements. That is in contrast with natrolite, which is ideally only sodium, and scolecite, which is ideally only calcium. Typically in zeolites there is a range of ionic replacement (most often Na, Ca, and K) but mesolite is said to have a pretty consistent chemistry such that microprobe can be used for identification. Walker and Parsons also say that it is easily distinguished from natrolite, scolecite, and thomsonite using a polarizing microscope. They note that those species show easily observable birefringence while mesolite is practically isotropic. Wet-chemical analyses by How (1858) and by Walker and Parsons (1922) are shown below, along with an electron microprobe analysis by Pe-Piper (2002). The asterisk by the water value in the Pe-Piper analysis indicates it is calculated by difference, as the microprobe cannot measure water. In comparison to mesolite from other world localities, the Walker and Parsons analysis appears in Hey (1933).

Table 2: Chemistry of mesolite from the North Mountain.

An X-ray diffraction pattern for mesolite from Kings County (XRD Pattern 529) is kept in the national database (Bonardi and Traill 1975). The largest peaks are [d-spacing in Å (intensity) 2-theta]: 6.46(50)13.9, 5.86(70)15.4, 4.67(40)19.3, 4.37(70)20.6, 2.86(100)31.5.

Montmorillonite - (Na,Ca)_0.33(Al,Mg)₂(Si₄O₁₀)(OH)₂·n(H₂O)

This is a smectite group mineral; a group that also includes nontronite and saponite. These are clay-like minerals, sometimes described as "swelling" or "expandable" clay minerals. It was identified on a specimen associated with gyrolite - Canadian Museum of Nature specimen CMNMC 40536 - pictured under the gyrolite section of this page.

Mordenite - (Na₂,Ca,K₂)Al₂Si₁₀O₂₄·7(H₂O)

In 1858, Henry How discovered a new zeolite to the east of Black Rock. He named it mordenite, for the small community of Morden, which was nearby. How says of the mineral,

It occurs in rather small masses, varying in size from the size of a pigeon's to that of a bantam's egg, in the form of somewhat cylindrical, reniform, or flattened geodes and solid concretions, rather smooth externally, sometimes coated with a thin, yellowish crust, blotched with a green mineral, probably a silicate of iron, and sometimes exposing its own white, yellowish, or pinkish-coloured surface; often a small portion of the latter only is visible.

Walker (1922) reports that mordenite is found from Harbourville to Chute Cove, with the best localities being "to the west of Margaretville and for a couple of miles to the east of Morden". Interestingly, he goes on to say,

The writer spent several days in the localities where How obtained the type material, and found only a very small amount of mordenite. It is a matter of surprise that How suspected the individuality of this mineral and that he was able without the aid of heavy solutions or thin sections for microscopic examination to secure material sufficiently pure to permit him to indicate the fundamental properties of his new mineral.

In a subsequent visit, Walker and Parsons (1924) report that mordenite was found at a few other nearby localities including White Water Brook and Chipman Brook, for a quarter mile west of Hall's Harbour and as radiating masses up to an inch in diameter in reddish basalt halfway between Murray Brook and Black Rock.

Pirsson (1890) wrote that experts long thought that How's analysis was incorrect because of the high percentage of silica. They thought he mistakenly analyzed a mixture of some other mineral and quartz. However, Pirsson and others went on to confirm How's discovery. It is one of the highest-silica zeolites known. It has since been found as fabulous specimens of hairlike needles from other parts of the world, but at this locality, display specimens cannot be found. Instead the material is restricted to massive fillings of small vugs, often intergrown with other minerals.

A summary of some chemical analyses of mordenite from the North Mountain is given in Table 3. The data for How is an average of five measurements. Walker and Parsons give a second analysis but it was possibly mixed with a second unknown zeolite so it has been left out. The values for Pe-Piper are an average of ten measurements. The first two columns are wet chemical and the Pe-Piper (2000) data is microprobe, with water given here by difference. Coombs et al. (1997) say the ratio Na/(Na+Ca) is typically in the range 0.50 to 0.81; this ratio has been calculated and added at the bottom of the table in blue. A couple of these values are high but the range is not a hard limit and there is always some experimental uncertainty.

Table 3: Chemistry of mordenite from the North Mountain.

Along with microprobe results, Pe-Piper (2000) also includes an electron micrograph of a mordenite crystal, reproduced below. Optical measurements on local mordenite are reported by Larsen (1921) using a specimen originally in the Roebling collection, which later became the nucleous of the Smithsonian.

Okenite - CaSi₂O₅·2H₂O

Walker and Parsons (1922) report the following:

One specimen of this mineral was collected from the trap about half a mile east of Morden in Kings County. It was part of a concretion about two and a half inches in diameter, and apart from a very narrow margin filled the whole cavity. It is exceedingly compact and very tough, hardness about 5, specific gravity 2.333, and white in colour. In thin sections under the microscope the mineral is seen to be composed of an exceedingly fine felt of fibres devoid of crystal boundaries. The principal impurity consists of small spherules of a colourless uniaxial mineral, probably gyrolite or apophyllite. These spherules appear to form by alteration of the okenite, which is very closely related chemically to the above mentioned minerals. So far as I am aware, this is the first discovery of okenite in Nova Scotia.

In the years since that report there are no other reports of the mineral. In 2019, I did some reading on gyrolite and okenite, and other calcium silicates found at other basalt localities in the world. This information suggested that a good place to look might be the harder, less mineralized basalt found deeper in the lava flow that would have stayed hot longer than the amygdaloidal surface layers.

Specimens were collected at both Canada Creek and Black Rock that turned out to be likely okenite, based on EDS and powder XRD (remaining discrepancies include some magnesium in the EDS and a couple missing peaks in the XRD). Material from Canada Creek was sent for additional testing in 2021 (EDS and Raman) where okenite was confirmed. This EDS gave (atomic percent) 64% Si and 36% Ca, close to the ideal (67% and 33%).

The fact that two specimens were found on the first trip, based on the new place to look, suggests that it might be more common, but was overlooked because it was not as interesting as the larger veins and pockets a couple meters higher in the rock.

Pyrite - FeS₂

A couple specimens (one massive and one crystal) were found in 2021 just northeast of T.R.'s Cove, near Sandy Cove, Digby County. The crystal was in a small pocket with platy (probably) quartz, in a very dark colored rock. It was collected in situ, so it was not glacial float. This is, I believe, the first report of pyrite from the North Mountain Formation in Nova Scotia. The crystal was a lustrous octahedron.

Quartz - SiO₂

Quartz is uncommon in this area. In the 1970's, a large find of quartz var. amethyst was found at Hall's Harbour in a farmer's field. Eldon George of Parrsboro collected large quantities and until recently, had a very large specimen on display at his shop/museum. The crystals on the specimen were very large for Nova Scotia and the color was a good medium purple. Smaller finds of amethyst are still made along the shore. In some cases the color is very saturated, as in the specimen below. Quartz, including amethyst is also reported from St. Mary's Bay (SW of Digby) (Jackson and Alger 1829) including a large specimen weighing more than 40 pounds of excellent color saturation and surrounded with a thin coat of fortification agate.

In the early 2000s a small find of some very different quartz was made in another field. This quartz was called caramel quartz for the light brown color. Under the scope the quartz is fantastic, with moss or worm-like inclusions of an unidentified mineral. These inclusions give the quartz its color. Visually, the unknown appears to be limonite, though it could also be a clay mineral. It is also interesting to note that these crystals show the Cumberland habit, which is when the prism faces are missing. Instead the crystals are pseudo-hexagonal bipyramids.

There is very little evidence of pseudomorphism, or any species, along this shore with the notable exception of hematite ps. magnetite from near Digby. Another example of pseudomorphism is shown below, of quartz pseudomorphs after stilbite. The crystal aggregates have an oval outline and fan equally from the sides and ends to form a dimple - similar to the shape of a Werther's candy. This is an unusual shape for stilbite, but similarly shaped aggregates, still as stilbite, have been found not far from the pseudomorphs. These specimens were collected by Terry Collett.

White chalcedony is commonly found below other minerals such as quartz. The example below is unusual in that the silica has formed on top of (i.e. after) the heulandite, suggesting a low temperature of formation as the heulandite is not altered in any way. The specimen is nearly pure SiO2, as confirmed by WDS. However, it is unclear if the material is chalcedony or opal. SOme additional tests will be required. On this specimen the material is brilliant white and hard. Another specimen was found, also of nearly pure SiO2, but not on top of zeolite, that was soft and perhaps weathered. In both cases, SEM images showed that the material had an almost Styrofoam-like structure, made on little balls. This would seem to be consistent with opal.

I'm not an agate collector exactly, so I don't know what all the areas have to offer for agate. It seems that straw agate, fortification agate, and lace agate can be found as well as gray and blue chalcedony. The areas closer to Digby seem to produce a nice variety of agates, but I can't say more than that.

Scolecite - CaAl₂Si₃O₁₀·3(H₂O)

Walker and Parsons (1922) report scolecite from the east side of Digby Gut as creamy white radiating masses to about 10 cm. Identification is supported by chemical and optical analyses. Pe-Piper (2002) reports it from Arlington Quarry using XRD and electron microprobe.

The Canadian Museum of Nature has a large XRD-confirmed specimen (CMNMC 39328). This specimen is recorded to have come from Ward’s Scientific and also has a label from the Williams College Collection (MA USA). The locality is simply Nova Scotia, but it could be from the Digby area. It is quite large and bright white but has only rough terminations.

Stilbite-Ca - NaCa₄Al₈Si₂₈O₇₂·30(H₂O)

It becomes clear why stilbite is Nova Scotia's provincial mineral when you walk these shores. Stilbite is very common found in nearly every cavity. Stilbite takes on several different habits in this area. Hemispherical mounds of stilbite, up to about 10 cm across, have been found. In contrast, very sharp individual blades are also common. Druses, sheaves and other shapes can also be found. The stilbite may be colorless, white, or creamy in color. It is nearly always associated with heulandite. The stilbite is usually found growing on the heulandite though sometimes heulandite is found on stilbite.

Stilbite aggregates tend to be quite different than at places such as Wasson's Bluff. Imagine a long bladed single stilbite crystal, at Wasson's the crystal aggregates fan out from each end of the blade, forming a bowtie shape. At Harbourville, the aggregates fan out from the long edges of the blade. This form is shown below.

An X-ray diffraction pattern for stilbite from Kings County (XRD Pattern 771) is kept in the national database (Bonardi and Traill 1975). The largest peaks are [d-spacing in Å (intensity) 2-theta]: 4.65(50)19.4, 4.07(100)22.1, 3.40(40)26.5, 3.04(70)29.6, 2.78(40)32.4.

Thomsonite-Ca - NaCa₂Al₅Si₅O₂₀·6(H₂O)

Though not abundant, the region around Margaretsville is a good locality for thomsonite. It has been found here since the mid 1800s when it was first reported from Port George by How under the now-obsolete name faröelite. Chemical analyses have been performed by both How and Walker and Parsons. It is found as fans and wheels, balls, and plates. These are often very nicely crystallized. The thin rectangular crystals (lath shaped, or length >> width >> thickness) are best appreciated under the microscope.

The balls reach about 1 cm in size and the plates can reach small cabinet size, though the crystal aggregates are still small. The color is white to creamy white and they show good translucency. The plates and larger pieces that I have seen are sometimes associated with (or intergrown with) mesolite. This is a very typical association for thomsonite.

Wise and Tschernich (1978) write that thomsonite and mesolite are commonly associated, but that most silica-rich thomsonite does not occur with mesolite. They also write that the Si/Al ratio influences the habit, with a lower ratio (1.05) producing coarse blades and higher ratios (1.13) producing fine blades. At the highest ratios (1.2-1.3), thomsonite forms botryoidal waxy balls of the faroelite variety. East of Margaretsville, the thomsonite is often associated with mesolite. The blades are very fine but still discrete, suggesting a moderate Si/Al ratio. It would be interesting to perform some modern analyses on these to learn what the ratio really is. However, we can look at How's analysis of faroelite (1858) from Port George. In that case the Si/Al ratio is 1.19, at the higher end of the range, in agreement with very very fine crystals.

In 2020, Rod Tyson collected some larger balls inland at Glenmont that reached several centimeters in size, approaching the largest thomsonites even from Cape D'Or. Those are quite large for the species. They are associated with a number of other species such as heulandite, chabazite, and analcime.

Unknown 1

In 2021, a small pocket of heulandite on quartz was collected. The heulandite was white and the rind of the pocket was massive quartz with a scalloped exterior, similar to what is often seen with amethyst pockets and veins. In a few spots between the heulandite was a brilliant white clay mineral. It may be montmortillonite, which is described earlier on this page, or it might be new. A similar white clay mineral was also found in 2021 from the outside of an amethyst vein at Cape Split. Neither have been identified at this time.

Unknowns 2 and 3

A rock was found east of Margaretsville in 2021 (see the entry for malachite) with a black submetallic mineral and a more silvery metallic one. There was some alteration in places to malachite. They are likely cuprite, which can sometimes have a metallic luster, and/or copper sulfides. Neither have been identified at this time.

Unknown 4

This unknown is also on the same piece as Unknowns 2 and 3. This mineral is blue-green in color - the color alone distinguishes it as a new mineral for this area. It forms good but very tiny crystals in a pocket associated with quartz, malachite, red cuprite, and one of the other unknowns. The color looks like langite or wroewolfeite, both hydrates copper sulfates but I cannot see crystal shape well enough to draw any further conclusions.

Unknown 5

This unknown forms beige tabular, simple short hexagonal prisms. The crystals are found in groups in pockets with sharp lustrous hematites, both covered in a white clay except where the pockets have been exposed and the clay weathered away. The rock is very unusual with numerous tiny pockets making the bulk rock low density. The color is very pale gray with a pink hue, likely due to hematite.

Conclusions

The south side of the Bay of Fundy has long provided many excellent specimens of zeolites and associated minerals. Heulandite and stilbite are nearly ubiquitous but many other species are also found, including mordenite, which was first discovered from here. Erosion continues to expose new pockets and sections of vein, making this a good spot for future collecting. As always, collecting along the Bay of Fundy requires an appreciation for the huge tides, but with a little safety forethought, these beaches make a great outing.

Acknowledgements

Special thanks to the archives of the Kings College library for the image of Henry How, to Pete Richards for the heulandite crystal drawing, to Judy and Mark Amirault for the club collecting-trip photo and to Terry Collett for allowing me to photograph specimens from his collection. Also thanks to Tim Fedak and the Nova Scotia Museum of Natural History for allowing me to photograph and share photos of their specimens, and to Georgia Pe-Piper for allowing me to photograph the epistilbite. Finally thanks to Xiang Yang and Saint Mary's University for the okenite analysis and SEM image.

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Disclaimer: This page is intended for information purposes only. The locality is not necessarily open to collecting. The locality is not necessarily safe.