Crystals
Peridot
Peridot • gem variety of olivine (forsterite–fayalite series) Formula: (Mg,Fe)2SiO4 • Idiochromatic (Fe2+ gives the green) Crystal system: Orthorhombic • Cleavage: poor/indistinct • Toughness: fair Mohs: ~6.5–7 • SG: ~3.3...
Peridot
Peridot • gem variety of olivine (forsterite–fayalite series) Formula: (Mg,Fe)2SiO4 • Idiochromatic (Fe2+ gives the green) Crystal system: Orthorhombic • Cleavage: poor/indistinct • Toughness: fair Mohs: ~6.5–7 • SG: ~3.3...
Orthocera
Orthoceras (often sold as “Orthocera”) • Fossil straight‑shelled nautiloid Group: Cephalopoda → Nautiloidea → Orthocerida Geologic age: chiefly Ordovician–Devonian (~485–359 Ma) Shell: straight orthocone • chambered with central siphuncle Common...
Orthocera
Orthoceras (often sold as “Orthocera”) • Fossil straight‑shelled nautiloid Group: Cephalopoda → Nautiloidea → Orthocerida Geologic age: chiefly Ordovician–Devonian (~485–359 Ma) Shell: straight orthocone • chambered with central siphuncle Common...
Unakite
Unakite • metamorphosed granite (rock), not a single mineral Typical mix: pink orthoclase feldspar + green epidote + clear/grey quartz Mohs (aggregate): ~6–7 • SG: ~2.6–2.9 • Luster: granular vitreous...
Unakite
Unakite • metamorphosed granite (rock), not a single mineral Typical mix: pink orthoclase feldspar + green epidote + clear/grey quartz Mohs (aggregate): ~6–7 • SG: ~2.6–2.9 • Luster: granular vitreous...
Topaz
Topaz • aluminum fluoro‑hydroxyl silicate — Al₂SiO₄(F,OH)₂ Crystal system: Orthorhombic • Habit: prismatic, often striated; water‑worn pebbles in gravels Mohs: 8 • SG: ~3.49–3.57 • Luster: vitreous Colors: colorless, yellow‑brown,...
Topaz
Topaz • aluminum fluoro‑hydroxyl silicate — Al₂SiO₄(F,OH)₂ Crystal system: Orthorhombic • Habit: prismatic, often striated; water‑worn pebbles in gravels Mohs: 8 • SG: ~3.49–3.57 • Luster: vitreous Colors: colorless, yellow‑brown,...
Sodalite
Sodalite • feldspathoid group — Na₈(Al₆Si₆O₂₄)Cl₂ Crystal system: Isometric (cubic) • Habit: massive, granular, rare dodecahedral crystals Mohs: ~5.5–6 • SG: ~2.27–2.40 • Luster: vitreous to greasy Cleavage: poor; Fracture:...
Sodalite
Sodalite • feldspathoid group — Na₈(Al₆Si₆O₂₄)Cl₂ Crystal system: Isometric (cubic) • Habit: massive, granular, rare dodecahedral crystals Mohs: ~5.5–6 • SG: ~2.27–2.40 • Luster: vitreous to greasy Cleavage: poor; Fracture:...
Silicon
Silicon • Element Si • metalloid • Group 14 Atomic no. 14 • Atomic mass ≈ 28.085 • Crystal: diamond‑cubic (sp³ network) Melting 1414 °C • Boiling 3265 °C • Density ~2.33 g/cm³...
Silicon
Silicon • Element Si • metalloid • Group 14 Atomic no. 14 • Atomic mass ≈ 28.085 • Crystal: diamond‑cubic (sp³ network) Melting 1414 °C • Boiling 3265 °C • Density ~2.33 g/cm³...