Scapolite in Bancroft Ontario – Fluorescent Wernerite, Meionite and Marialite 

​What is Scapolite?

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The scapolites (from the Greek words for “rod” and “stone”) are a group of rock-forming silicate minerals. Their main elements are aluminum, calcium, sodium, and silica, along with varying amounts of chlorine, carbonate, and sulfate.

 

Fluorescent Scapolite Discoveries Near Gooderham Ontario

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Rummaging around in the rock pile that was excavated from a nearby roadcut just south of Gooderham Mark found a chunk of massive meionite (scapolite end member) that literally glows as bright as a lantern. A discussion on mindat suggests there is no such fluorescence on local scapolite, but we beg to differ. Some suggest the fluorescent material is from Quebec, but this rock dump is from local road cuts. Too often experts challenge whats outside their experience as improbable. Anything is possible in an area like Bancroft.

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There can be a significant difference in fluorescence between the Bancroft scapolite varieties, Meionite and Marialite, but its not specifically due to any structural underpinnings. The intensity of fluorescence in Scapolite is controlled more by trace chemistry and structural defects than by the primary chemistry alone.

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In general, meionite-rich scapolite is much more likely to fluoresce strongly, often producing bright yellow, orange, or cream colors under UV light, while sodium-rich marialite is commonly weakly fluorescent or completely inert. This difference is thought to result from the carbonate-bearing structure of meionite, which more readily accommodates sulfur substitutions and lattice defects that activate fluorescence. Intermediate scapolite varieties commonly referred to as “wernerite” in the Bancroft region often show the strongest fluorescence because they contain mixed carbonate and chlorine chemistry along with sulfur-bearing components such as silvialite. This likely explains why some Gooderham-area scapolite glows brilliantly while similar-looking Bear Lake material may show little to no UV response. Weathering can also reduce fluorescence over time, so freshly broken surfaces often glow much more intensely than altered outer surfaces.

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Scapolite Chemistry – From Marialite to Meionite

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Being a continuous series, the chemistry through the series is pretty standard with a transition from sodium rich marialite (Na4Al3Si9O24Cl) to calcium rich meionite (Ca4Al6Si6O24CO3). Local mineral traders call the meionite “wernerite” after a German mineralogist. Being on a continuum the content of scapolite varies with the location, but to be wernerite the crystal ratio, meionite to marialite must be between 3 and 2:1, so I suppose you can say that wernerite is an intermediate scapolite in the tetragonal system with long blocky columns. Initially, based on specimens from Norway, wernerite was thought to have been a separate mineral species but as chemical analysis improved wernerite was discovered to be a form of scapolite.

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As metamorphism becomes more intense with higher heat and pressure, scapolite tends to transition to the calcium end of the series - more meionite, than the Na rich marialite. Scapolite formed in high-pressure environments is usually rich in calcium. The middle varieties of scapolite, which have a balanced aluminum-to-silicon ratio, form at lower temperatures and are commonly found in clay-rich limestones and evaporite rocks that have slowly changed during metamorphism.

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​Although much of Ontario is known for calcium-rich metamorphic rocks, there are also examples of sodium-rich metamorphic environments, especially within the Grenville Province. In the Bancroft area, sodium-rich rocks and minerals are associated with albite-bearing gneisses, altered pegmatites, and alkaline intrusions. Localities to the east and north west of Bancroft have produced rocks containing albite, nepheline, sodalite, and scapolite with a stronger marialite component. Think of cancrinite Hill and the Princess sodalite mine. These sodium-rich conditions are thought to have formed through the influence of saline fluids and alkaline magmas during metamorphism. Ontario also contains occurrences of sodium-rich amphiboles such as glaucophane and riebeckite, which indicate unusual metamorphic conditions involving elevated sodium content and pressure.

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​The Dark Star “Feldspar Fissure” Scapolite Discovery

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Now that brings us to a spot on the Dark Star claim that we had initially called “The Feldspar Fissure” as at its discovery the mineral that was being found there was thought to be feldspar. In truth, looking at the prisms they are 4 sided and striated up their length. The 4 sidedness seems to have 90 degree corners and the striations are a result of several possible situations, they are listed below.

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Why Scapolite Crystals Have Striations

 

• Layered crystal growth — Scapolite commonly grows in pulses as temperature, pressure, or chemistry changes. Each slight growth episode can leave tiny ridges or grooves parallel to the crystal’s long axis.

• Internal crystal structure — Scapolite has a tetragonal crystal system, and its atomic arrangement naturally favors elongation along one direction. This can produce repeated parallel growth steps on prism faces.

• Alternating chemistry — Scapolite is actually a series between marialite (sodium-rich) and meionite (calcium-rich). Small shifts in chemistry during growth may create uneven growth rates that appear as fine striations.

• Contact metamorphic conditions — In places like the Bancroft region, scapolite often forms in high-temperature metamorphosed limestones and gneisses. Fluids moving through the rock during crystallization can promote rhythmic crystal growth and pronounced prism markings.

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Either way the striations are pronounced and clearly an identifying feature of scapolite. scapolite's striations are irregularly spaced at times and way thicker than I have seen on tourmaline - besides tourmaline has a 3 sided bulging prism, scapolite is w 4 sided and in this weathered version- chalky on the outside.

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Silvialite and UV Reactive Scapolite

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Another recognized member of the group is silvialite, which contains both calcium and sodium along with sulfate and carbonate components. Together, these minerals form a continuous series with varying chemical compositions. It is the sulfur that causes the fluorescence. Oddly bear Lake material is not known to fluoresce and it was this that initially threw me off in the identification. I had expected that fantastic yellow light that had come from Mark’s Gooderham sample, but just nothing here but a washed out grey.

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Scapolite Crystal Habit and Appearance

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Scapolite minerals commonly form tetragonal crystals that appear as square or rectangular columns with well-defined prism faces. These crystals can sometimes grow to impressive sizes and are usually white, greyish-white, or opaque in appearance. Most of the material that we have harvested so far from the feldspar fissure (wrongly named) has prisms varying between 1 and 3 inches thick. In some cases the prisms are bent like a banana, multiple fractures across the prisms indicate breakage and rehealing.

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Transparent Scapolite Crystals from the Dark Star Fissure

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In some rare cases, such as meionite crystals found near Mount Vesuvius in Italy, they can occur as clear and glassy crystals. Cristin found a beautiful translucent scapolite point yesterday and uncovered several similar specimens still attached to the fissure wall. Looking at the overall composition of the fissure, its actually two parallel fissures with scapolite predominantly on the right side and an igneous intrusion up the center that divides both fissures. From the right fissure a hole that we widened from 6 inches to two feet leads underground to a shelf that slopes down under "fissure city" at an angle of about 30 degrees. No doubt this space has been sealed since the fissures formed over a billion years ago. A roof that is absolutely packed with tetragonal crystals awaits our inspection when the shelf is more safely accessed.

 

Hammering down in the calcite infilling on the right side a hole was soon opened up into a low downward sloping shelf. I found an almost transparent crystal on the roof of the shelf, extracting it with my fingers and gifting it to the person I was digging with. I’m sure there is more to come, we just have to find a safe way to enter beneath the shelf.

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Scapolite Hardness, Specific Gravity and Cleavage

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Scapolite has a hardness of about 5 to 6 on the Mohs scale, and its specific gravity varies depending on composition, ranging from about 2.5 to 2.7. These are simple tests that can be conducted at home though SG can be confusing as it overlaps with feldspar SG. Cleavage is a little more telling as feldspar will have relatively straight cleavage planes along a break. Scapolite is more granular.

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Weathering and Alteration of Scapolite

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One notable feature of scapolite is that it is highly susceptible to weathering and alteration. Over time, exposure to fluids and environmental conditions can transform scapolite into minerals such as mica or kaolin, often causing the crystals to lose their transparency and become cloudy or opaque. Because of these alterations and the wide range of chemical compositions possible within the group, many different varieties and trade names of scapolite have been identified throughout mineralogical history.

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Feldspar Replacement and Scapolite Transformation

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A relatively common scapolite transformation  that is referred to as “scapolitization” is where plagioclase is replaced by scapolite thus retaining the external shape of plagioclase but chemically and physically becoming scapolite. In this situation hot fluids are introduced to the feldspar setting along planes of weakness such as cracks or cleavages and chlorine, carbon and sulfur are incorporated into the crystal, but the aluminum and silicon ratios remain the same.

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In scapolitization, precipitation and solution occur at a somewhat even rate, the solution of feldspar occurring to remove the feldspar and then the solution being super-saturated dropping the elements for the conversion. Within a feldspar crystal it is possible to see the scapolitization change spidering along cleavage planes or cracks. The transformation creeps in slowly along points of weakness like a wave front and porosity channels carry fluids to the front of where the transformation is taking place. The end result is that patches of feldspar are left isolated by the spreading scapolite networks.

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Marialite Formation Reaction from Albite

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So a sodium rich feldspar with the addition of so more sodium and chlorine becomes Marialite, the sodium end member of the scapolite series in a proportion of 3 units of feldspar to one of sodium and chlorine.

A simplified end-member reaction is:

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3NaAlSi3O8+NaCl→Na4Al3Si9O24Cl

Where:

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• NaAlSi3O8 = albite

• NaCll = chlorine-bearing fluid

• Na4Al3Si9O24Cl = marialite

 

Meionite Formation Reaction from Anorthite

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The transformation toward Meionite usually involves calcium-rich plagioclase reacting with carbonate-bearing material during metamorphism.

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A simplified end-member reaction is:

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3CaAl2Si2O8+CaCO3→Ca4Al6Si6O24CO3

Where:

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• CaAl2Si2O8 = anorthite (calcium plagioclase)

• CaCO3 = calcite

• Ca4Al6Si6O24CO3 = meionite

 

How to Identify Meionitic Scapolite in the Field

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Field signs that scapolite may be more meionitic include:

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• cream to gray coloration,

• association with calcite or diopside,

• stronger reaction environments near marbles,

• higher SG than sodium-rich marialite,

• occasional orange fluorescence under UV, but weathering reduces this over time.

 

The presence of grains and areas of varying translucency within our Dark Star scapolites might indicate partial transformation. Some tend to have distinctly feldspar looking cores – not sugary, but appearing to have flat cleavage surfaces.

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Scapolite in Limestones and Contact Metamorphic Rocks

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Scapolite is commonly found in limestones and contact metamorphic rocks, especially where impure limestone has been altered by the heat and fluids of nearby igneous intrusions. Because scapolite minerals are rich in calcium, they naturally develop in these environments alongside minerals such as calcite, epidote, garnet, vesuvianite, wollastonite, diopside, and amphibole. Even marialite, the sodium-rich variety of scapolite, can form in these settings and has been discovered in small crystals within volcanic limestone blocks from areas such as Mount Vesuvius in Italy and the Eifel volcanic region of Germany. Scapolite crystals are typically colorless, flesh-colored, grey, or greenish, though some may appear nearly black due to tiny inclusions of graphite.

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Why Diopside Forms With Wernerite

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Diopside forms in calcium-rich metamorphic environments, especially where silica is available but not in excess. In calc-silicate rocks, diopside crystallizes alongside scapolite because:

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• both require calcium-rich chemistry,

• both form at high metamorphic temperatures,

• both are stable in marble and skarn-like settings.

 

Where scapolite is forming from feldspar + carbonate + fluid interaction, diopside often crystallizes in nearby zones where silica and calcium are balanced differently. This is why they commonly appear together in the same rock packages, sometimes even intergrown.

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Why Titanite Is So Common With Wernerite

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Titanite (sphene) forms under similar metamorphic conditions but requires an additional ingredient: titanium. In the Grenville rocks around Bancroft, titanium is present in trace amounts in:

• amphibolite,

• biotite,

• and mafic intrusive rocks.

 

During metamorphism, titanium becomes mobilized in fluids and crystallizes as titanite in calcium-rich environments—the same environments where scapolite is forming. Titanite is especially stable in:

• calc-silicate assemblages,

• marble contacts,

• and metasomatized gneiss zones.

 

So titanite and wernerite often grow together simply because both depend on calcium-rich metamorphic fluids, even though titanite incorporates titanium while scapolite incorporates chlorine or carbonate.

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The Key Link: Calc-Silicate Metasomatism

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The real connection between all three minerals is a process called calc-silicate metasomatism, where hot fluids chemically transform rocks by adding and redistributing elements. In these systems:

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• feldspar → scapolite (wernerite/marialite-meionite series),

• silica + calcium → diopside,

• calcium + titanium → titanite.

 

These reactions often happen in the same fracture zones, marble contacts, or fissures—exactly the kind of setting found in Bancroft collecting sites.

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Wernerite, diopside, and titanite are associated in Bancroft because they all form from the same high-grade metamorphic fluid systems acting on calcium-rich rocks. They are essentially different “products” of the same geological process—each recording slightly different chemical conditions within the same evolving calc-silicate environment of the Grenville Province.

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Scapolite Crystal Occurrences Around the World

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Although well-formed crystals do occur, scapolite is more commonly found as small grains scattered throughout crystalline limestones and calc-silicate rocks. Over time, weathering can alter scapolite into micaceous materials or other secondary minerals. In some thermally altered calcareous shales, especially those affected by strong contact metamorphism, larger and more well-formed crystals may develop. These crystals can sometimes reach lengths of one or two inches and are often seen as imperfect octagonal prisms. Thus far the crystal at the Dark Star Crystal mines are very large and rough, in rare cases a small patch of golden iridescence appears on the surface of a prism.

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Pyrenees Mountain Scapolite Deposits and Formation

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In the Pyrenees Mountains, extensive zones of limestone intruded by igneous rocks such as diabase and peridotite contain abundant scapolite occurrences. In these areas, scapolite appears both in the limestones and in associated calcareous shales. Some crystals are clear, while others are filled with tiny inclusions of minerals like augite, tourmaline, and biotite from the surrounding rock matrix. A dark variety containing fine graphitic inclusions is especially well known from these localities and is commonly referred to as couzeranite or dipyre. Geologists believe that the presence of small amounts of chlorine within the limestone may help promote the formation of scapolite during metamorphism.

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Conclusion – Scapolite at Dark Star Crystal Mines

 

In the end, scapolite has proven to be far more than the “feldspar” we first believed it to be. From the glowing meionite of Gooderham to the massive striated prisms emerging from the Dark Star fissure, these minerals tell a story of heat, fluids, fracture systems, and slow chemical transformation deep within the Grenville rocks of the Bancroft region. Their varied chemistry, unusual fluorescence (or lack of  it), and tendency to replace feldspar while preserving crystal form make scapolites both scientifically fascinating and visually striking. As we continue exploring the fissure system and uncovering new translucent crystals hidden within the calcite shelves, it is becoming increasingly clear that the Dark Star occurrence may represent one of the more interesting local scapolite discoveries we have encountered, with much still waiting to be revealed beneath the surface.

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Frequently Asked Questions About Scapolite

 

What is scapolite?

Scapolite is a group of silicate minerals that commonly form in metamorphic and igneous rocks. It is best known for its elongated prismatic crystals, striated crystal faces, and colors ranging from white and gray to yellow, violet, and pink. In the Bancroft area of Ontario, scapolite is often associated with calcite, diopside, titanite, and feldspar.

 

Where is scapolite found in Ontario?

Some of the best-known Ontario occurrences are located near Bancroft, including the Bear Lake region and other metamorphic terrains of the Grenville Province. These deposits formed during intense regional metamorphism and are popular with mineral collectors and rockhounds.

 

Why are some scapolite crystals transparent?

Transparent scapolite crystals usually form in stable environments where crystals can grow slowly with few internal fractures or inclusions. Gem-quality scapolite is often found in calcium-rich metamorphic rocks, especially where crystal growth occurred in open spaces or coarse crystalline marble.

 

What is the difference between meionite and marialite?

Meionite and marialite are the two main end members of the scapolite mineral series. Meionite is richer in calcium, while marialite contains more sodium. Most natural scapolite specimens fall somewhere between the two compositions, creating intermediate varieties commonly referred to as wernerite.

 

Does scapolite fluoresce under ultraviolet light?

Yes. Some scapolite specimens display strong fluorescence under UV light, often glowing yellow, orange, pink, or red depending on their chemistry and trace elements. Fluorescent scapolite from the Bancroft region is especially prized by collectors of Ontario minerals.

 

Bio - Michael Gordon (author of this article)

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Michael Has been a rockhound since childhood. He has a degree in geography from the University of Guelph, a diploma in gemology and a certification as a professional diamond grader. Some of you might be familiar with his 3-part rockhound series (books)  which is available on this site; he is also curator of the YouTube channel "Caver461".

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References:

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Ontario Geological Survey. 1997. Geology and Scenery, Peterborough, Bancroft and Madoc Area. Toronto: Ontario Ministry of Northern Development and Mines.

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Grice, J. D. 1989. Famous Mineral Localities of Canada. Special Publication 3. Montreal: Mineralogical Association of Canada.

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Sabina, A. P. 1986. Rocks and Minerals for the Collector: Bancroft–Parry Sound Area. Miscellaneous Report 39. Ottawa: Geological Survey of Canada.

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Satterly, J. 1977. Mineral Locality Catalogue of Ontario (ROM Collections). Toronto: Ontario Geological Survey.

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Ontario Geological Survey. n.d. Mineral Deposit Inventory records for Bancroft area scapolite occurrences (e.g., Lower Faraday Road). Queen’s Printer for Ontario.

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Breaks, F. W., and A. E. Moore. 1992. Geology of the Grenville Province and Its Mineral Deposits. Ottawa: Geological Survey of Canada.

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Robinson, P., and R. A. Wilson. 2010. Mineralogy and Metamorphic Evolution of the Grenville Orogen in Ontario. Ottawa: Geological Survey of Canada Bulletin.

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Last updated 2026