Crystals
Apache tear
Rounded nodules of natural obsidian Silica-rich rhyolitic volcanic glass Amorphous rather than crystalline Mohs approximately 5–5.5 Warm brown translucency in strong backlight Conchoidal fracture and exceptionally sharp fresh edges Apache...
Apache tear
Rounded nodules of natural obsidian Silica-rich rhyolitic volcanic glass Amorphous rather than crystalline Mohs approximately 5–5.5 Warm brown translucency in strong backlight Conchoidal fracture and exceptionally sharp fresh edges Apache...
Lapis lazuli
Lazurite-rich metamorphic rock (Na,Ca)8(AlSiO4)6(S,SO4,Cl)2 Sodalite-group framework Bulk hardness commonly about 5–5.5 Brassy pyrite inclusions White calcite veins and clouds Ultramarine from sulfur radical anions Historic source: Badakhshan, Afghanistan Lapis Lazuli:...
Lapis lazuli
Lazurite-rich metamorphic rock (Na,Ca)8(AlSiO4)6(S,SO4,Cl)2 Sodalite-group framework Bulk hardness commonly about 5–5.5 Brassy pyrite inclusions White calcite veins and clouds Ultramarine from sulfur radical anions Historic source: Badakhshan, Afghanistan Lapis Lazuli:...
Crazy lace agate
Chalcedony Banded agate SiO2 Mohs 6.5–7 Classic source: Mexico Crazy Lace Agate: Warm Ribbons, Earth-Drawn Lace, and Steady Joy Crazy Lace Agate is a patterned variety of chalcedony admired for...
Crazy lace agate
Chalcedony Banded agate SiO2 Mohs 6.5–7 Classic source: Mexico Crazy Lace Agate: Warm Ribbons, Earth-Drawn Lace, and Steady Joy Crazy Lace Agate is a patterned variety of chalcedony admired for...
Crinoide fossil
Marine echinoderm Class Crinoidea Ordovician to Recent Calcite skeleton Commonly CaCO3; sometimes silicified Crinoid Fossils: Sea Lilies, Columnal Stars, and the Architecture of Ancient Seas Crinoids are marine animals related...
Crinoide fossil
Marine echinoderm Class Crinoidea Ordovician to Recent Calcite skeleton Commonly CaCO3; sometimes silicified Crinoid Fossils: Sea Lilies, Columnal Stars, and the Architecture of Ancient Seas Crinoids are marine animals related...
Epidote
Calcium aluminum iron sorosilicate Monoclinic crystal system Mohs approximately 6–7 Strong pleochroism Ca2Al2(Fe3+,Al)(SiO4)(Si2O7)O(OH) Epidote: Pistachio-Green Crystals of Metamorphism, Fluids, and Change Epidote is an iron-bearing calcium aluminum silicate recognized by...
Epidote
Calcium aluminum iron sorosilicate Monoclinic crystal system Mohs approximately 6–7 Strong pleochroism Ca2Al2(Fe3+,Al)(SiO4)(Si2O7)O(OH) Epidote: Pistachio-Green Crystals of Metamorphism, Fluids, and Change Epidote is an iron-bearing calcium aluminum silicate recognized by...
Howlite
Calcium borate mineral Ca2B5SiO9(OH)5 Monoclinic crystal system Massive material: Mohs approximately 3.5 White, chalky, or porcelaneous nodules Frequently dyed blue or green Howlite: Porcelain-White Borate, Ink Veins, and the Science...
Howlite
Calcium borate mineral Ca2B5SiO9(OH)5 Monoclinic crystal system Massive material: Mohs approximately 3.5 White, chalky, or porcelaneous nodules Frequently dyed blue or green Howlite: Porcelain-White Borate, Ink Veins, and the Science...