Heliotrope (mineral)
The mineral aggregate heliotrope (from Ancient Greek ἥλιος (hḗlios) 'sun', and τρέπειν (trépein) 'to turn'), also known as bloodstone or ematille, is a cryptocrystalline mixture of [quartz] that occurs mostly as jasper (opaque) or sometimes as chalcedony (translucent). The "classic" bloodstone is opaque green jasper with red inclusions of hematite. The red inclusions may resemble spots of blood, hence the name bloodstone.
| Heliotrope | |
|---|---|
A heliotrope, also known as a bloodstone | |
| General | |
| Category | Mineral |
| Formula (repeating unit) | SiO2 (silicon dioxide) |
| Crystal system | Trigonal |
| Identification | |
| Color | Green with red or yellow spots |
| Mohs scale hardness | 6.5–7 |
| Luster | Vitreous |
| Specific gravity | 2.61 |
| Refractive index | 1.53–1.54 |
| Birefringence | 0.004 |
The name heliotrope derives from various ancient notions about the manner in which the mineral reflects light. Such notions are described, for example, by Pliny the Elder (Nat. Hist. 37.165).
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