Crystals
Peridot
Gem variety of olivine (Mg,Fe)2SiO4 Orthorhombic nesosilicate Mohs 6.5–7 Idiochromatic yellow-green Strong double refraction Upper mantle and pallasites August birthstone Peridot: Green Light from Earth’s Mantle Peridot is the transparent...
Peridot
Gem variety of olivine (Mg,Fe)2SiO4 Orthorhombic nesosilicate Mohs 6.5–7 Idiochromatic yellow-green Strong double refraction Upper mantle and pallasites August birthstone Peridot: Green Light from Earth’s Mantle Peridot is the transparent...
Orthocera
Fossil straight-shelled cephalopod Commercial names: Orthoceras and “Orthocera” True Orthoceras: Middle Ordovician Baltoscandia Common decorative material: Silurian–Devonian Morocco Chambered orthocone with siphuncle Calcite fossil in dark limestone Matrix hardness approximately...
Orthocera
Fossil straight-shelled cephalopod Commercial names: Orthoceras and “Orthocera” True Orthoceras: Middle Ordovician Baltoscandia Common decorative material: Silurian–Devonian Morocco Chambered orthocone with siphuncle Calcite fossil in dark limestone Matrix hardness approximately...
Unakite
Unakite • metasomatically altered granitic rock Pink potassium feldspar • commonly orthoclase or microcline Green epidote • commonly replacing plagioclase Colorless to smoky-gray quartz Coarse-grained, mottled, massive, or weakly foliated...
Unakite
Unakite • metasomatically altered granitic rock Pink potassium feldspar • commonly orthoclase or microcline Green epidote • commonly replacing plagioclase Colorless to smoky-gray quartz Coarse-grained, mottled, massive, or weakly foliated...
Topaz
Topaz • orthorhombic nesosilicate Al2SiO4(F,OH)2 Mohs 8 • specific gravity about 3.49–3.57 Perfect basal cleavage on {001} Vitreous luster • biaxial positive Commonly prismatic with vertical striations Imperial colors range...
Topaz
Topaz • orthorhombic nesosilicate Al2SiO4(F,OH)2 Mohs 8 • specific gravity about 3.49–3.57 Perfect basal cleavage on {001} Vitreous luster • biaxial positive Commonly prismatic with vertical striations Imperial colors range...
Sodalite
Sodalite group feldspathoid Na8(Al6Si6O24)Cl2 Isometric crystal system Rare dodecahedra; commonly massive or granular Mohs 5.5–6 Specific gravity about 2.27–2.33 White material is commonly calcite or feldspathic matrix Fluorescence may be...
Sodalite
Sodalite group feldspathoid Na8(Al6Si6O24)Cl2 Isometric crystal system Rare dodecahedra; commonly massive or granular Mohs 5.5–6 Specific gravity about 2.27–2.33 White material is commonly calcite or feldspathic matrix Fluorescence may be...
Silicon
Silicon, element symbol Si Atomic number 14 Group 14 metalloid Standard atomic weight 28.085 Diamond-cubic crystal structure Density about 2.33 g/cm³ Melting point about 1414 °C Indirect band gap about...
Silicon
Silicon, element symbol Si Atomic number 14 Group 14 metalloid Standard atomic weight 28.085 Diamond-cubic crystal structure Density about 2.33 g/cm³ Melting point about 1414 °C Indirect band gap about...