Crystals
Serpentine
Serpentine • mineral group (antigorite • lizardite • chrysotile) Formula: ~Mg₃Si₂O₅(OH)₄ with Fe/Ni substitutions • Polytypes: monoclinic & trigonal Hardness: ~2.5–5.5 • SG: ~2.55–2.65 • Luster: waxy to silky Look:...
Serpentine
Serpentine • mineral group (antigorite • lizardite • chrysotile) Formula: ~Mg₃Si₂O₅(OH)₄ with Fe/Ni substitutions • Polytypes: monoclinic & trigonal Hardness: ~2.5–5.5 • SG: ~2.55–2.65 • Luster: waxy to silky Look:...
Selenite
Selenite • a crystalline variety of Gypsum (CaSO₄·2H₂O) Crystal system: Monoclinic • Cleavage: perfect on one plane Hardness: ~2 (yes, a fingernail can scratch it) • SG: ~2.3 Varieties in...
Selenite
Selenite • a crystalline variety of Gypsum (CaSO₄·2H₂O) Crystal system: Monoclinic • Cleavage: perfect on one plane Hardness: ~2 (yes, a fingernail can scratch it) • SG: ~2.3 Varieties in...
Sardonyx
Sardonyx • banded chalcedony (SiO₂: microcrystalline quartz) Parallel bands: sard (red‑brown) + onyx (white/black) Mohs ~6.5–7 • SG ~2.58–2.64 • Luster: waxy‑to‑vitreous Classic for cameos, intaglios & signet rings Sardonyx...
Sardonyx
Sardonyx • banded chalcedony (SiO₂: microcrystalline quartz) Parallel bands: sard (red‑brown) + onyx (white/black) Mohs ~6.5–7 • SG ~2.58–2.64 • Luster: waxy‑to‑vitreous Classic for cameos, intaglios & signet rings Sardonyx...
Sapphire
Sapphire • Corundum (Al₂O₃) — all colors except red (ruby) Crystal system: Trigonal • Habit: hexagonal barrels, bipyramids Hardness: 9 • SG: ~3.95–4.05 • Luster: vitreous Optics: RI ~1.762–1.770 •...
Sapphire
Sapphire • Corundum (Al₂O₃) — all colors except red (ruby) Crystal system: Trigonal • Habit: hexagonal barrels, bipyramids Hardness: 9 • SG: ~3.95–4.05 • Luster: vitreous Optics: RI ~1.762–1.770 •...
Tektite
Tektite • natural impact glass — terrestrial melt ejected by meteorite impacts Structure: Amorphous (glass) • Habit: splash forms (drop, dumbbell, disc, button), etched/sculpted surfaces Mohs: ~5–6 • SG: ~2.20–2.50...
Tektite
Tektite • natural impact glass — terrestrial melt ejected by meteorite impacts Structure: Amorphous (glass) • Habit: splash forms (drop, dumbbell, disc, button), etched/sculpted surfaces Mohs: ~5–6 • SG: ~2.20–2.50...
Stromatolite
Stromatolite • laminated microbialite — fossilized microbial mats that trap & bind sediment or precipitate minerals Morphology: planar, domal, columnar, conical; related forms: oncoids (spherical), thrombolites (clotted) Composition (varies): carbonate...
Stromatolite
Stromatolite • laminated microbialite — fossilized microbial mats that trap & bind sediment or precipitate minerals Morphology: planar, domal, columnar, conical; related forms: oncoids (spherical), thrombolites (clotted) Composition (varies): carbonate...