Hessonite
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| Hessonite | |
|---|---|
 Striated crystals of hessonite
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| General | |
| Category | variety of the grossular species |
| Chemical formula | Ca3Al2Si3O12 |
| Identification | |
| Crystal system | cubic[1] |
| Cleavage | none, sometimes indistinct parting[1] |
| Fracture | conchoidal to uneven[1] |
| Mohs Scale hardness | 7 |
| Polish luster | vitreous[1] |
| Optical Properties | Single refractive, often anomalous double refractive [1] |
| Birefringence | none[1] |
| Pleochroism | none[1] |
| Specific gravity | 3.64 to 3.69 |
Hessonite or Cinnamon Stone is a variety of grossular, a calcium aluminium mineral of the garnet group with the general formula Ca3Al2Si3O12. The name is from the Greek hēssōn, inferior, in allusion to its lower hardness and density than most other garnet species varieties.
It has a characteristic red color, inclining to orange, much like that of gem zircon. Indeed it was shown many years ago, by Sir A. H. Church, that many gems, especially engraved stones, commonly regarded as zircon, were really hessonite. The difference is readily detected by the specific gravity, that of hessonite being 3.64 to 3.69, whilst that of zircon is about 4.6. Hessonite has a similar hardness to that of quartz, about 7 on the mohs scale, whilst the hardness of most garnet species can reach 7.5.
Hessonite comes chiefly from Sri Lanka, where it is found generally in placer deposits, though its occurrence in its native matrix is not unknown. It is also found in Brazil and California.
[edit] References
- Mineral galleries
- This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
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