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Scapolite

Scapolite is also known as wernerite named after the German geologist, A.G. Werner, scapolite ranges in color from pink, purple, blue, yellow and grey to colourless. These colors reflect the variation in composition, from sodium-rich to calcium-rich. Crystals are found as prisms that resemble sticks, giving rise to the name “scapolite”, derived from the Greek words scapos, meaning rod, and lithos, meaning stone.

Scapolite is silicate of aluminium with calcium and sodium where potassium or fluorine may be present. Scapolite comes in almost all colors (yellow and violet are common) and is a good simulant for many natural stones including quartz, beryl, feldspar, etc.

Scapolite is found as crystals in pegmatites and metamorphic rocks like mica schist and gneiss. It also occurs in massive form. Localities include Brazil, Burma, Canada, Kenya and Madagascar.

A cat’s-eye effect can be seen in some pink and purple stones. Scapolite may easily be confused with amblygonite, chrysoberyl, and golden beryl.

A scapolite is cut into cabochon when parallel needle like inclusions is found within it so that it can generate cat’s eye effect otherwise it is cut in facetted cut stone. The best scapolite come form Kenya, Madagascar, Brazil and Tanzania.

Cause of Color : Color centers.
Chemical Composition :

Silicate of aluminium with calcium and sodium. Potassium or fluorine may be present.


Classification / Type :

Belongs to the Marialite (sodium rich) – Meionite (calcium rich) isomorphous series. As a result there is a wide range in properties and composition.


Crystal System / Forms :

Tetragonal System / Prismatic crystals with square cross-section, massive cleavage material.


Cuts & Uses :

Facetted cuts.


Dispersion : 0.017
Hardness : 6
Lustre : Vitreous.
Magnification :

Parallel rod like cavities, needles, crystal and fluid inclusions, may show doubling.


Optic Character :

Anisotropic, D.R.; Uniaxial Negative.


Pleochroism : Distinct
Refractive Index / Birefringence :

1.535 – 1.542 / 0.007; 1.550 – 1.572 / 0.022. Range: 1.535 – 1.572. R.I. increases with meionite percentage. As R.I. increases birefringence increases and vice-versa.


Simulants (with separation tests) :

Quartz (optic figure / sign, U.V. fluorescence, inclusions, doubling), feldspar (optic figure, inclusions), beryl (R.I., birefringence, U.V. fluorescence, inclusions), Iolite (optic figure, pleochroism, U.V. fluorescence), Glass (optic character)


Sources :

Kenya, Madagascar, Brazil, Myanmar, Tanzania, Canada.


Specific Tests :

Attacked by acids.


Spectrum :

Red, pink, violet: band at 663nm and 652nm, absorption in yellow.


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