Crystals
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...
Quartz
Silicon dioxide SiO2 Trigonal crystal system at ordinary conditions Hexagonal prisms with rhombohedral terminations Mohs hardness 7 Specific gravity about 2.65 Uniaxial positive and optically active Piezoelectric and widely used...
Quartz
Silicon dioxide SiO2 Trigonal crystal system at ordinary conditions Hexagonal prisms with rhombohedral terminations Mohs hardness 7 Specific gravity about 2.65 Uniaxial positive and optically active Piezoelectric and widely used...
Pyrite
Iron disulfide FeS2 Cubic crystal system Cubes, pyritohedra, octahedra, and combinations Mohs hardness 6–6.5 Specific gravity about 5.0 Metallic brass-yellow luster Greenish-black to brownish-black streak Hydrothermal, sedimentary, igneous, and metamorphic...
Pyrite
Iron disulfide FeS2 Cubic crystal system Cubes, pyritohedra, octahedra, and combinations Mohs hardness 6–6.5 Specific gravity about 5.0 Metallic brass-yellow luster Greenish-black to brownish-black streak Hydrothermal, sedimentary, igneous, and metamorphic...