Garnet
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Garnet | |
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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]
- ↑ a b 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.