Kristalopedia
Orthocera
Orthoceras (often sold as "Orthocera") • Fossil straight-shelled nautiloid Group: Cephalopoda → Nautiloidea → Orthocerida Geological age: mostly Ordovician–Devonian (~485–359 million years ago) Shell: straight orthocone • chambered with central...
Orthocera
Orthoceras (often sold as "Orthocera") • Fossil straight-shelled nautiloid Group: Cephalopoda → Nautiloidea → Orthocerida Geological age: mostly Ordovician–Devonian (~485–359 million years ago) Shell: straight orthocone • chambered with central...
Orange calcite
Orange calcite • CaCO₃ — calcite (carbonate group) Crystal system: trigonal (rhombohedral) • Cleavage: perfect in 3 directions (rhombohedral) Mohs: ~3 • SG: ~2.71 • Luster: vitreous (pearly on cleavage...
Orange calcite
Orange calcite • CaCO₃ — calcite (carbonate group) Crystal system: trigonal (rhombohedral) • Cleavage: perfect in 3 directions (rhombohedral) Mohs: ~3 • SG: ~2.71 • Luster: vitreous (pearly on cleavage...
Meteorites
Meteorite • Extraterrestrial rock (stony • stony–iron • iron) Typical age: ~4.56 billion years (Solar System times) Key features: fusion crust • regmaglypts (“thumbprints”) • metal flakes • chondrules Density:...
Meteorites
Meteorite • Extraterrestrial rock (stony • stony–iron • iron) Typical age: ~4.56 billion years (Solar System times) Key features: fusion crust • regmaglypts (“thumbprints”) • metal flakes • chondrules Density:...
Porphyra
Porphyritic texture • Magmatic rock texture (phenocrysts in a fine matrix) Two-stage cooling: slow → phenocrysts • fast → aphanitic groundmass Phenocrysts: feldspar, quartz, hornblende, pyroxene ± olivine Mohs scale:...
Porphyra
Porphyritic texture • Magmatic rock texture (phenocrysts in a fine matrix) Two-stage cooling: slow → phenocrysts • fast → aphanitic groundmass Phenocrysts: feldspar, quartz, hornblende, pyroxene ± olivine Mohs scale:...
Opals
Opal • hydrated amorphous silicon dioxide (SiO₂·nH₂O) Structure: silicon dioxide spheres + water • amorphous (opal‑A/AG) Mohs ~5–6.5 • SG ~1.98–2.25 Luster: vitreous to waxy • Fracture: conchoidal Phenomenon: play...
Opals
Opal • hydrated amorphous silicon dioxide (SiO₂·nH₂O) Structure: silicon dioxide spheres + water • amorphous (opal‑A/AG) Mohs ~5–6.5 • SG ~1.98–2.25 Luster: vitreous to waxy • Fracture: conchoidal Phenomenon: play...
Obsidian
Obsidian • Volcanic glass (mineraloid) Chemistry: silica-rich melt (rhyolite) • SiO₂ ~70–78% Mohs ~5–5.5 • SG ~2.3–2.45 Fracture: conchoidal (very sharp) Phenomena/varieties: snowflake • vitreous • rainbow • mahogany •...
Obsidian
Obsidian • Volcanic glass (mineraloid) Chemistry: silica-rich melt (rhyolite) • SiO₂ ~70–78% Mohs ~5–5.5 • SG ~2.3–2.45 Fracture: conchoidal (very sharp) Phenomena/varieties: snowflake • vitreous • rainbow • mahogany •...