Silicates: Tremolite-Actinolite

Composition: Ca₂(Mg,Fe)₅(Si₈O₂₂)(OH,F)₂; the name tremolite is used for the pale-colored iron-poor variety, the name actinolite is used for the dark-colored iron-rich variety

Crystal system: Monoclinic; fibrous aggregates or finegrained masses

5.32.1
tremolite crystals in quartz

Properties:

• Vitreous lustre
• White to dark green color depending on iron content
• White streak
• Knife barely scratches or not at all (Mohs Hardness 5-6)
• Average to above average density depending on iron content
• Two cleavages not at right angles to each other
• Cleaves rather than fractures
• Not ferromagnetic
• Does not react with hydrochloric acid (HCl)

Occurrence:

Tremolite and actinolite occur in low grade metamorphic rocks and in some hydrothermal vein and replacement ore deposits.

5.32.2 tremolite crystals in quartz	5.32.3 actinolite crystals in talc

Nephrite jade is a finegrained massive variety of actinolite that is used for ornaments and sculptures.