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The Mineral scapolite

White Scapolite Crystal Grouping

Scapolite is a mineral series consisting of two very similar minerals: sodium-rich Marialite and calcium-rich Meionite. The two Scapolites also differ in that Meionite has a carbonate radical in place of chlorine that is present in Marialite. The two Scapolite minerals are often visibly indistinguishable from each other, and they also form unclassified intermediary examples within their series. Scapolite is the accepted term that encompasses both minerals, and further classification into Marialite or Meionite is often not done unless the species determination is absolute.

Scapolite forms as an alteration mineral of the feldspars. It can form in two entirely different and unrelated habits, as large and stocky white, opaque crystals, and as prismatic, completely transparent gemmy crystals in elongated form.

For additional information, see the gemstone section on Scapolite.

Chemical Formula

Marialite: Na₄(Al₃Si₉O₂₄)Cl
Meionite: Ca₄(Al₆Si₉O₂₄)(CO₃)

Color

White, gray, colorless, cream, yellow, bluish-gray, and purple. Less commonly blue, brown, green, red, and pink.

Crystal System

Tetragonal

Properties

Streak
White

Hardness
5 - 6

Transparency
Transparent to opaque

Specific Gravity
2.5 - 2.8

Luster
Vitreous to dull

Cleavage
2,2

Fracture
Conchoidal, uneven

Tenacity
Brittle

Other ID Marks
Often fluorescent, sometimes brightly. Colors include white, yellow, and pink. Fluorescence may be present both in shortwave and longwave.

Crystal Habits

Crystals are often short and stout with a slightly angled or pyramidal termination, or long and prismatic. Crystals can be very large and fat, and are often intergrown in groups of such crystals or are columnar. Also grainy, massive, and crudely as formed crystal masses. Prismatic crystals are often striated.

3D Crystal Atlas

Additional Information

Composition
Marialite: Sodium aluminum chloro-silicate
Meionite: Calcium aluminum carbonate-silicate
Within the series, sodium and calcium are fully interchangeable. The chlorine and carbonate are also interchangeable, and are occasionally replaced partially with a sulfate radical.

In Group
Silicates; Tectosilicates

Striking Features
Crystal habit, environment, and fluorescence.

Environment
Chiefly in metamorphic rocks, such as metamorphosed limestones, skarns, gneisses, and hornfels. Also in granite pegmatites and volcanic rocks such as basalt.

Rock Type
Igneous, Metamorphic

Varieties

Nuttalite

- Variety of Scapolite with a gray color (and possibly a tint of purple or blue) with slight chatoyancy.

Petschite

- Trade name for purple Scapolite from Tanzania.

Wernerite

- A variety or synonym of Scapolite. This term is often used to describe a strongly fluorescent form of Scapolite, especially the greenish-gray to material described from Quebec, Canada. The term Wernertite may also be used to describe an intermediary member between Marialite and Meionite.

Uses

The gemmy clear crystals of Scapolite are important collector minerals, especially when they exhibit a good size and color. These transparent forms are also cut as rare collectors gemstones.

Noteworthy Localities

Although Scapolite is fairly common mineral, several localities stand out for producing excellent specimens of gemmy, transparent examples of this mineral. Beautiful purple crystals come from Afghanistan at Badakhshan Province; and at Dara-i-Pech, Konar Province. Light purple Scapolite comes from Muzeinaya, Kukh-i-Lal, Tajikistan; and pale yellow crystals from Karur, Tamil Nadu, India.

Colorless and yellow Scapolite is found in the marble region of Mogok, Burma (Myanmar), and transparent yellows crystals come from Tanzania in the Merelani Hills, Arusha; and in Morogoro, Uruguru. Transparent, light yellow crystals come from Antananarivo and Tuléar Provinces, Madagascar; and colorless, elongated crystals from Linópolis, Doce valley, Minas Gerais, Brazil.

In the U.S., fairly large white Scapolite crystals have come from Franklin, Sussex Co., New Jersey; Amity and Twin Lakes in Woodbury, Orange Co., New York; and Pierrepont and Rossie, St. Lawrence Co., New York. In Canada, excellent crystals come from the Bancroft area, Ontario; and from Diamond Lake, Herschel Township, Ontario. Good Scapolite was found in Gooderham, Haliburton Co., Ontario; and a strongly fluorescent Scapolite with a bright yellow fluorescence, comes from Grenville-sur-la-Rouge, Québec, associated with blue-fluorescing Diopside.