Garnet
| Garnet | |
|---|---|
 |
|
| General | |
| Category | Nesosilicate |
| Formula (repeatin unit) |
The general formula X3Y2(SiO4)3 |
| Creestal seestem | Cubic rhombic dodecahedron, icositetrahedron |
| Identification | |
| Colour | virtually aw colours |
| Creestal habit | Rhombic dodecahedron or cubic |
| Cleavage | Indistinct |
| Fractur | conchoidal tae uneven |
| Mohs scale haurdness | 6.5–7.5 |
| Skinkle | vitreous tae resinous |
| Streak | White |
| Speceefic gravity | 3.1–4.3 |
| Polish skinkle | vitreous tae subadamantine[1] |
| Optical properties | Single refractive, eften anomalous double refractive[1] |
| Refractive index | 1.72–1.94 |
| Birefringence | None |
| Pleochroism | None |
| Major varieties | |
| Pyrope | Mg3Al2Si3O12 |
| Almandine | Fe3Al2Si3O12 |
| Spessartine | Mn3Al2Si3O12 |
| Andradite | Ca3Fe2Si3O12 |
| Grossular | Ca3Al2Si3O12 |
| Uvarovite | Ca3Cr2Si3O12 |
Garnets /ˈɡɑːrnət/ are a group o silicate meenerals that hae been uised syne the Bronze Age as gemstanes an abrasives.[note 1]
Aw species o garnets possess seemilar pheesical properties an crystal forms, but differ in chemical composition. The different species are pyrope, almandine, spessartine, grossular (varieties o which are hessonite or cinnamon-stane an tsavorite), uvarovite an andradite. The garnets mak up twa solid solution series: pyrope-almandine-spessarite an uvarovite-grossular-andradite.
Notes[eedit | eedit soorce]
- ↑ The wird garnet comes frae 14t‑century Middle Inglis wird gernet meanin 'dark reid,' frae the Laitin granatus, frae granum ('grain, seed') + suffix atus, possibly a reference tae mela granatum or even pomum granatum ('pomegranate',[2] scientific name: Punica granatum), a plant whose fruits contain abundant an vivid reid arils, are similar in shape, size, an colour tae some garnet crystals.[3]
References[eedit | eedit soorce]
- ↑ 1.0 1.1 Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
- ↑ pomegranate. Online Etymology Dictionary. Retrieved on 2011-12-25.
- ↑ garnet. Online Etymology Dictionary. Retrieved on 2011-12-25.
