Crystals
Rhodonite
Rhodonite • pyroxenoid — idealized (Mn,Fe,Mg,Ca)SiO₃ (Mn‑dominant) Crystal system: Triclinic • Habit: massive, granular, cleavable pieces; rare prismatic crystals Mohs: ~5.5–6.5 • SG: ~3.4–3.7 • Cleavage: perfect in two directions...
Rhodonite
Rhodonite • pyroxenoid — idealized (Mn,Fe,Mg,Ca)SiO₃ (Mn‑dominant) Crystal system: Triclinic • Habit: massive, granular, cleavable pieces; rare prismatic crystals Mohs: ~5.5–6.5 • SG: ~3.4–3.7 • Cleavage: perfect in two directions...
Rhodochrosite
Rhodochrosite • MnCO₃ — manganese carbonate (calcite group) Crystal system: Trigonal (rhombohedral) • Habit: rhombohedra, scalenohedra, botryoidal & stalactitic bands Mohs: ~3.5–4 • SG: ~3.5–3.7 • Cleavage: perfect rhombohedral in...
Rhodochrosite
Rhodochrosite • MnCO₃ — manganese carbonate (calcite group) Crystal system: Trigonal (rhombohedral) • Habit: rhombohedra, scalenohedra, botryoidal & stalactitic bands Mohs: ~3.5–4 • SG: ~3.5–3.7 • Cleavage: perfect rhombohedral in...
Quartz
Quartz • SiO₂ • Tectosilicate (framework silicate) Crystal system: Trigonal (α‑quartz) • Habit: prismatic with pyramids Hardness ~7 • SG ~2.65 • Luster: vitreous • Cleavage: none Optics: Uniaxial (+)...
Quartz
Quartz • SiO₂ • Tectosilicate (framework silicate) Crystal system: Trigonal (α‑quartz) • Habit: prismatic with pyramids Hardness ~7 • SG ~2.65 • Luster: vitreous • Cleavage: none Optics: Uniaxial (+)...
Pyrite
Pyrite • FeS2 • Iron disulfide (sulfide mineral) Crystal system: Isometric (cubes, pyritohedra, combinations) Color: brass‑yellow (“fool’s gold”) • Luster: metallic Hardness: ~6–6.5 • SG: ~5.0 • Streak: greenish‑black Cleavage:...
Pyrite
Pyrite • FeS2 • Iron disulfide (sulfide mineral) Crystal system: Isometric (cubes, pyritohedra, combinations) Color: brass‑yellow (“fool’s gold”) • Luster: metallic Hardness: ~6–6.5 • SG: ~5.0 • Streak: greenish‑black Cleavage:...
Prehnite
Prehnite • Ca2Al(AlSi3O10)(OH)2 — calcium‑aluminum phyllosilicate Crystal system: Orthorhombic • Habit: botryoidal “grapes,” stalactitic, radial crusts, rare tabular crystals Mohs: ~6–6.5 • SG: ~2.8–2.95 • Luster: vitreous to pearly on...
Prehnite
Prehnite • Ca2Al(AlSi3O10)(OH)2 — calcium‑aluminum phyllosilicate Crystal system: Orthorhombic • Habit: botryoidal “grapes,” stalactitic, radial crusts, rare tabular crystals Mohs: ~6–6.5 • SG: ~2.8–2.95 • Luster: vitreous to pearly on...
Porphyry
Porphyry • Igneous texture (phenocrysts in fine matrix) Two‑stage cooling: slow → phenocrysts • fast → aphanitic groundmass Phenocrysts: feldspar, quartz, hornblende, pyroxene ± olivine Mohs: ~6 (feldspar) to 7...
Porphyry
Porphyry • Igneous texture (phenocrysts in fine matrix) Two‑stage cooling: slow → phenocrysts • fast → aphanitic groundmass Phenocrysts: feldspar, quartz, hornblende, pyroxene ± olivine Mohs: ~6 (feldspar) to 7...