Heliotrope (mineral)
Mineral aggregate / From Wikipedia, the free encyclopedia
The mineral aggregate heliotrope (from Ancient Greek ἥλιος (hḗlios) 'sun', and τρέπειν (trépein) 'to turn'), also called Indian bloodstone or ematille, is a cryptocrystalline mixture of quartz that occurs mostly as jasper (opaque) or sometimes as chalcedony (translucent). The "classic" bloodstone is translucent to opaque green chalcedony and red jasper that contains inclusions of hematite. The red jasper may resemble spots of blood, hence the name bloodstone. Other colors of chalcedony also can occur in Indian bloodstone, such as white, yellow, or blue. This stone should not be confused with other ornamental stones that contain red jasper, such as Setonite (also known as African Bloodstone) which is composed of red jasper, grey chalcedony, and pyrite; or Dragon's Blood (sometimes referred to as Australian Bloodstone) which is composed of red jasper and green epidote.
Heliotrope | |
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A tumble-polished pebble of heliotrope, also called bloodstone | |
General | |
Category | Silicate mineral |
Formula (repeating unit) | SiO2 (silicon dioxide) |
Crystal system | Trigonal |
Identification | |
Color | Dark shades of green, often with red or yellow spots; sometimes mixed with whitish silica |
Fracture | Conchoidal |
Mohs scale hardness | 6.5–7 |
Luster | Vitreous |
Diaphaneity | Opaque to translucent |
Specific gravity | 2.61 |
Refractive index | 1.53–1.54 |
Birefringence | 0.004 |
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Bloodstone_4_%2849036280821%29.jpg/640px-Bloodstone_4_%2849036280821%29.jpg)
The name heliotrope derives from ancient beliefs about the manner in which the mineral reflects light. Such notions are described, for example, by Pliny the Elder (Nat. Hist. 37.165).[1]