Actinolite
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- For the Sailor Moon character, see Shitennou.
| Actinolite | |
|---|---|
 Well-cleaved, dark, fine-grained chlorite-actinolite metadiabase intrudes light granitic gneiss
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| General | |
| Category | Mineral |
| Chemical formula | Ca2(Mg,Fe)5Si8O22(OH)2[1] |
| Identification | |
| Color | Transparent to opaque. Pale to dark green, yellowish green and black.[1] White or grey when in asbestos form |
| Crystal system | Monoclinic[1] |
| Cleavage | Perfect in two directions. [1] |
| Fracture | uneven[1] |
| Mohs Scale hardness | 5 - 6[1] |
| Luster | vitreous to dull[1] |
| Polish luster | vitreous [1] |
| Refractive index | 1.606 - 1.641 (+.014)[1] |
| Optical Properties | Double refractive with anomalous aggregate reaction, biaxial negative.[1] |
| Birefringence | .022 - .027[1] |
| Pleochroism | moderate, yellow to dark green (in stones that are transparent)[1] |
| Ultraviolet fluorescence | inert[1] |
| Absorption spectra | faint line at 503nm[1] |
| Specific gravity | 3.00 (+.10, -.05)[1] |
Actinolite is an inosilicate mineral with the chemical formula
Ca2(Mg,Fe)5Si8O22(OH)2
Contents |
[edit] Mineralogy
Actinolite is an intermediate member in a solid-solution series between tremolite (Mg-rich) and ferro-actinolite (Fe-rich) amphiboles. As seen from the chemical formula above, Mg and Fe ions can be freely exchanged in the crystal structure.
[edit] Occurrence
Actinolite is commonly found in metamorphic rocks, such as contact aureoles surrounding cooled intrusive igneous rocks. It also occurs as a product of metamorphism of magnesium-rich limestones.
The old mineral name uralite is at times applied to an alteration product of primary pyroxene by a mixture composed largely of actinolite. The metamorphosed gabbro or diabase rock bodies, referred to as epidiorite, contain a considerable amount of this uralitic alteration.
Some forms of asbestos are formed from fibrous actinolite, the fibres being so small that they can enter the lungs and damage the alveoli.
[edit] Gemology
Some forms of actinolite are used as gemstones. The first is called nephrite, which is one of the two types of jade (the other being jadeite a variety of pyroxene).[1]
Another gem variety of actinolite is the chatoyant form known as cat's-eye actinolite. This stone is translucent to opaque, and green to yellowish green color. This variety has had the misnomer jade cat's-eye.[1] Transparent actinolite is rare and is faceted for gem collectors.[1] Major sources for these forms of actinolite are Taiwan, and Canada.[1] Other sources are Madagascar, Tanzania, and the US.[1]
[edit] Related minerals
[edit] References
- ^ a b c d e f g h i j k l m n o p q r s t (Gia), Gemological. Gem Reference Guide. City: Gemological Institute of America (GIA), 1988. ISBN 0-87311-019-6
- Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
- Mindat.org
- Webmineral.org
- Mindat - uralite
