Kristalopedia
Mahogany obsidian
Mahogany obsidian • Volcanic glass (mineraloid) Chemistry: silica-rich melt (rhyolite) Mohs ~5–5.5 • SG ~2.3–2.45 Fracture: conchoidal • Luster: glassy Pattern: brown–mahogany swirls in black glass Mahogany obsidian — swirl...
Mahogany obsidian
Mahogany obsidian • Volcanic glass (mineraloid) Chemistry: silica-rich melt (rhyolite) Mohs ~5–5.5 • SG ~2.3–2.45 Fracture: conchoidal • Luster: glassy Pattern: brown–mahogany swirls in black glass Mahogany obsidian — swirl...
Ruby
Ruby • red corundum variety — Al₂O₃, colored by Cr³⁺ Crystal system: trigonal • Morphology: tabular / prismatic hexagonal forms, "barrel" crystals, granular aggregates Moh hardness: 9 • SG: ~3.99–4.05...
Ruby
Ruby • red corundum variety — Al₂O₃, colored by Cr³⁺ Crystal system: trigonal • Morphology: tabular / prismatic hexagonal forms, "barrel" crystals, granular aggregates Moh hardness: 9 • SG: ~3.99–4.05...
Silicis
Silicon • Element Si • metalloid • Group 14 Atomic no. 14 • Atomic mass ≈ 28.085 • Crystal lattice: diamond cubic (sp³ network) Melts at 1414 °C • Boils...
Silicis
Silicon • Element Si • metalloid • Group 14 Atomic no. 14 • Atomic mass ≈ 28.085 • Crystal lattice: diamond cubic (sp³ network) Melts at 1414 °C • Boils...
Peridots
Peridot • a gemstone variety of olivine (forsterite–fayalite series) Formula: (Mg,Fe)2SiO4 • Idiochromatic (Fe2+ gives a green color) Crystal system: orthorhombic • Cleavage: poor/unclear • Hardness: medium Mohs hardness: ~6.5–7...
Peridots
Peridot • a gemstone variety of olivine (forsterite–fayalite series) Formula: (Mg,Fe)2SiO4 • Idiochromatic (Fe2+ gives a green color) Crystal system: orthorhombic • Cleavage: poor/unclear • Hardness: medium Mohs hardness: ~6.5–7...
Pyrites
Pyrite • FeS2 • iron disulfide (sulfide mineral) Crystal system: cubic (cubes, pyritohedrons, combinations) Color: brass yellow ("fool's gold") • Luster: metallic Hardness: ~6–6.5 • SG: ~5.0 • Streak color:...
Pyrites
Pyrite • FeS2 • iron disulfide (sulfide mineral) Crystal system: cubic (cubes, pyritohedrons, combinations) Color: brass yellow ("fool's gold") • Luster: metallic Hardness: ~6–6.5 • SG: ~5.0 • Streak color:...
Moqui
"Moqui marbles" • iron oxide concretions Surface layer: Navajo sandstone (Jurassic), southwestern USA Composition: hematite (Fe2Or3) ± goethite around quartz sand cores Shapes: spheres • discs • rings ("spurs") •...
Moqui
"Moqui marbles" • iron oxide concretions Surface layer: Navajo sandstone (Jurassic), southwestern USA Composition: hematite (Fe2Or3) ± goethite around quartz sand cores Shapes: spheres • discs • rings ("spurs") •...