Heliotrope (mineral)

Heliotrope

A heliotrope, also known as a bloodstone.
General
Category Mineral
Formula
(repeating unit)		 SiO2 (silicon dioxide)
Identification
Color Green with red or yellow spots
Crystal system Trigonal
Mohs scale hardness 6.5–7
Luster Vitreous
Specific gravity 2.61
Refractive index 1.53–1.54
Birefringence 0.004

The mineral heliotrope, also known as bloodstone, is a form of chalcedony (which is a cryptocrystalline mixture of quartz and its monoclinic polymorph moganite). The "classic" bloodstone is green chalcedony with red inclusions of iron oxide or red jasper. Sometimes the inclusions are yellow, in which case the mineral is given the name plasma.

The red inclusions are supposed to resemble spots of blood; hence the name "bloodstone". The name "heliotrope" (from Greek ήλιος helios, Sun, τρέπειν trepein, to turn) derives from various ancient notions about the manner in which the mineral reflects light. These are described, e.g., by Pliny the Elder (Nat. Hist. 37.165). [1]

Heliotrope features in one of Boccaccio's stories in the Decameron.

Heliotrope is sometimes used in carved signet rings and is the traditional birthstone for March.

Sources

The primary source of the stone is India. It is also found in Brazil, China, Australia, and the United States. There is also an outcrop of bloodstone on the Isle of Rum, in Scotland.

References

  1. ↑ "heliotrope". Merriam-Webster Dictionary. m-w.com.

External links