Crystals
Angelite
Blue massive anhydrite CaSO4 Orthorhombic calcium sulfate Mohs approximately 3–3.5 Three prominent cleavages near 90° Dry storage and gentle handling Angelite: Powder-Blue Anhydrite, Right-Angled Cleavage, and the Memory of Evaporated...
Angelite
Blue massive anhydrite CaSO4 Orthorhombic calcium sulfate Mohs approximately 3–3.5 Three prominent cleavages near 90° Dry storage and gentle handling Angelite: Powder-Blue Anhydrite, Right-Angled Cleavage, and the Memory of Evaporated...
Ammonite
Extinct marine cephalopods Subclass Ammonoidea Early Devonian to end Cretaceous Originally aragonitic chambered shells Calcite, pyrite, silica, and internal molds Ammolite from preserved iridescent shell Ammonites: Chambered Cephalopods, Fossil Sutures,...
Ammonite
Extinct marine cephalopods Subclass Ammonoidea Early Devonian to end Cretaceous Originally aragonitic chambered shells Calcite, pyrite, silica, and internal molds Ammolite from preserved iridescent shell Ammonites: Chambered Cephalopods, Fossil Sutures,...
Chrysantemum
Composite ornamental rock Dark sedimentary matrix Calcite or aragonite: CaCO3 Celestine: SrSO4 Radial crystal aggregates Not a fossil flower Component-dependent hardness Chrysanthemum Stone: Mineral Flowers Written Through Dark Rock Chrysanthemum...
Chrysantemum
Composite ornamental rock Dark sedimentary matrix Calcite or aragonite: CaCO3 Celestine: SrSO4 Radial crystal aggregates Not a fossil flower Component-dependent hardness Chrysanthemum Stone: Mineral Flowers Written Through Dark Rock Chrysanthemum...
Amethyst
Purple variety of quartz SiO2 Trigonal crystal system Mohs 7 Iron-related color centers and irradiation Color-zoned points, clusters, geodes, and gems Amethyst: Violet Quartz, Color-Zoned Crystals, and the Quiet Architecture...
Amethyst
Purple variety of quartz SiO2 Trigonal crystal system Mohs 7 Iron-related color centers and irradiation Color-zoned points, clusters, geodes, and gems Amethyst: Violet Quartz, Color-Zoned Crystals, and the Quiet Architecture...
Chrysocolla
Variable hydrated copper silicate material Cyan, teal, and blue-green Oxidized copper deposits Usually massive or botryoidal Mohs approximately 2–4 when porous Up to quartz hardness when silica-rich Gem silica association...
Chrysocolla
Variable hydrated copper silicate material Cyan, teal, and blue-green Oxidized copper deposits Usually massive or botryoidal Mohs approximately 2–4 when porous Up to quartz hardness when silica-rich Gem silica association...
Chiastolite
Andalusite variety Al2SiO5 Orthorhombic Mohs approximately 6.5–7.5 Carbonaceous cross inclusions Low-pressure metamorphic indicator Pleochroic host mineral Chiastolite: Andalusite with a Cross Written Through Its Growth Chiastolite is an inclusion-rich variety...
Chiastolite
Andalusite variety Al2SiO5 Orthorhombic Mohs approximately 6.5–7.5 Carbonaceous cross inclusions Low-pressure metamorphic indicator Pleochroic host mineral Chiastolite: Andalusite with a Cross Written Through Its Growth Chiastolite is an inclusion-rich variety...