Crystals
Muscovite
Dioctahedral mica KAl2(AlSi3O10)(OH,F)2 Monoclinic, commonly 2M1 Perfect basal cleavage Mohs about 2–2.5 along the sheets Elastic transparent leaves Pearly to vitreous luster Fuchsite and fine white-mica forms Muscovite: The Shimmering...
Muscovite
Dioctahedral mica KAl2(AlSi3O10)(OH,F)2 Monoclinic, commonly 2M1 Perfect basal cleavage Mohs about 2–2.5 along the sheets Elastic transparent leaves Pearly to vitreous luster Fuchsite and fine white-mica forms Muscovite: The Shimmering...
Vesuvianite
Vesuvianite • traditional synonym: idocrase Representative formula: Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4 Complex calcium–aluminum sorosilicate Tetragonal • square-section prisms and stepped pyramids Mohs about 6–7 • specific gravity about 3.32–3.45 Vitreous to resinous •...
Vesuvianite
Vesuvianite • traditional synonym: idocrase Representative formula: Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4 Complex calcium–aluminum sorosilicate Tetragonal • square-section prisms and stepped pyramids Mohs about 6–7 • specific gravity about 3.32–3.45 Vitreous to resinous •...
Vanadinite
Vanadinite • lead chlorovanadate Pb5(VO4)3Cl Apatite supergroup • vanadate member Hexagonal • short prisms and barrel-shaped crystals Red, orange, yellow, and reddish brown Mohs about 2.5–3 • specific gravity about...
Vanadinite
Vanadinite • lead chlorovanadate Pb5(VO4)3Cl Apatite supergroup • vanadate member Hexagonal • short prisms and barrel-shaped crystals Red, orange, yellow, and reddish brown Mohs about 2.5–3 • specific gravity about...
Rhyolite
Felsic volcanic rock Commonly 69–80 wt% SiO2 Fine-grained or glassy equivalent of granitic composition Quartz, alkali feldspar, and plagioclase are characteristic Aphanitic, porphyritic, flow-banded, or brecciated Obsidian, perlite, pumice, and...
Rhyolite
Felsic volcanic rock Commonly 69–80 wt% SiO2 Fine-grained or glassy equivalent of granitic composition Quartz, alkali feldspar, and plagioclase are characteristic Aphanitic, porphyritic, flow-banded, or brecciated Obsidian, perlite, pumice, and...
Rhodonite
Manganese silicate CaMn3Mn[Si5O15] Rhodonite-group pyroxenoid Triclinic crystal system Five-tetrahedron silicate-chain repeat Mohs hardness 5.5–6.5 Specific gravity 3.57–3.76 Perfect cleavage in two near-perpendicular directions Rose-pink host with common manganese-oxide alteration Metamorphosed...
Rhodonite
Manganese silicate CaMn3Mn[Si5O15] Rhodonite-group pyroxenoid Triclinic crystal system Five-tetrahedron silicate-chain repeat Mohs hardness 5.5–6.5 Specific gravity 3.57–3.76 Perfect cleavage in two near-perpendicular directions Rose-pink host with common manganese-oxide alteration Metamorphosed...
Rhodochrosite
Manganese carbonate MnCO3 Calcite group · trigonal symmetry Rhombohedra, scalenohedra, stalactites, and botryoidal masses Mohs hardness 3.5–4 Specific gravity about 3.7 Perfect rhombohedral cleavage Uniaxial negative with very high birefringence...
Rhodochrosite
Manganese carbonate MnCO3 Calcite group · trigonal symmetry Rhombohedra, scalenohedra, stalactites, and botryoidal masses Mohs hardness 3.5–4 Specific gravity about 3.7 Perfect rhombohedral cleavage Uniaxial negative with very high birefringence...