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Compact Wollastonite Grouping
SILICATES; INOSILICATES · TRICLINIC

Wollastonite

CaSiO3

Hardness
4.5–5
Streak
White
Spec. Gravity
2.8–2.9
System
Triclinic

About

Wollastonite was named in honor William Hyde Wollaston (1766-1828), a British chemist and physicist noted for his inventions in optics. It is an important industrial mineral and is well known for its good fluorescence.

Crystal Forms & Aggregates

Other ID Marks

Complex Tests

Striking Features

Environment

Varieties

✓ common  · ✗ uncommon

Polymorphs

Wollastonite occurs in three different forms, depending on its crystallization. Common Wollastonite is known as Wollastonite 1A, indicating that it is one form of Wollastonite that crystallizes in the triclinic system. The "1A" distinguishes it from two rarer forms of Wollastonite, which are scientifically different minerals since they crystallize differently: Wollastonite 2M and Wollastonite 7A. Wollastonite 2M crystallizes in the monoclinic system, and Wollastonite 7A in the triclinic system but forms different crystals than Wollastonite 1A.

(Wollastonite 7A can be further divided into four additional minerals which are almost identical. They are Wollastonite 3A, 4A, 5A, and 7A.)

Additional names may be given to the variant forms of Wollastonite:

Wollastonite 1A Wollastonite
Wollastonite 2M Parawollastonite
Wollastonite 7A Pseudowollastonite

Both Wollastonite 2M and Wollastonite 7A are very rare. Most Wollastonite specimens are Wollastonite 1A.

Uses

Wollastonite is an industrially important mineral. It is a necessary ingredient in heat-resistant refractory ceramics and is used as a filler in paint. It is also used in the manufacture of paper and plastics.

Due to its fluorescece, Wollastonite is a popular mineral among collectors who specialize in fluorescent minerals.

Noteworthy Localities

European occurrences of Wollastonite include Monte Somma, Vesuvius, Italy; the Stanisław quarry, Świeradów Zdrój, Poland; and Pargas, Finland. In Canada, Wollastonite is found at the Jeffery Mine, Asbestos, Quebec.

In the U.S., Wollastonite occurs in California at the Crestmore Quarry, Riverside Co.; and the Lone Pine Mine, Independence, Inyo Co., California. Upstate New York contains several important deposits, including Natural Bridge; St. Lawrence Co.; the Rose Road Locality, near Pitcairn, St. Lawrence Co.; Lake Bonaparte and Diana, Lewis Co.; and Willsboro, Essex Co. Wollastonite that fluoresces a bright orange-yellow is well known at Franklin and Ogdensburg, Sussex Co., New Jersey.

Common Mineral Associations

Distinguishing Similar Minerals

Tremolite - Has different cleavage angles; otherwise can be difficult to distinguish
Pectolite - Crystals more compact and densely fibrous, and usually in different environments than Wollastonite.

Photos

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Crystal forms

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Prismatic Crystal
Tabular