Actinolite

Crystallography: Monoclinic, bladed crystals, usually elongated; fibrous, columnar aggregates; massive; granular; twinned.

Colors: Light to dark green, blackish green

Luster: Vitreous

Hardness: 5.5

Specific gravity: 3.05 - 3.44

Cleavage: 2 directions, good, often fibrous nature; brittle, compact variety tough.

Refractive index: 1.619 –1.644

Birefringence: 0.022 – 0.026

Pleochroism: yellow to dark green.

Spectrum: faint line at 503nm

Luminescence: none due to presence of iron.

Occurrence: Contact metamorphic limestones and dolomites.

Madagascar: small, dark green crystals.

Tanzania: transparent crystals.

USA

Stone sizes: Actinolite is rarely facetable and usually in small fragments. Material from Chester, Vermont, USA could provide large stones.

Comments: Chatoyant material is cut to exhibit cat’s eye phenomena. Actinolite is a constituent of nephrite jade; easy to cleave and difficult to cut—for this reason it may not be an ideal stone for jewelry. Quartz cat’s eye, Apatite cat’s eye, Chrysoberyl cat’s eye, Cathay stone (man-made glass) may be confused for Actinolite cat’s eye.