Crystals
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...
Hypersthene
Historical orthopyroxene name (Mg,Fe2+)2Si2O6 Orthorhombic pyroxene structure Mohs approximately 5–6 Bronze or silver directional schiller Two cleavages meeting near 90° Hypersthene: Bronze Schiller, Dark Orthopyroxene, and the Mineralogy of Quiet...
Hypersthene
Historical orthopyroxene name (Mg,Fe2+)2Si2O6 Orthorhombic pyroxene structure Mohs approximately 5–6 Bronze or silver directional schiller Two cleavages meeting near 90° Hypersthene: Bronze Schiller, Dark Orthopyroxene, and the Mineralogy of Quiet...
Iolite
Gem-quality cordierite (Mg,Fe)2Al4Si5O18 Orthorhombic and biaxial Mohs approximately 7–7.5 Violet-blue, blue-gray, and straw trichroism Cut orientation controls face-up color Iolite: Violet-Blue Cordierite, Three-Way Color, and the Geometry of Direction Iolite...
Iolite
Gem-quality cordierite (Mg,Fe)2Al4Si5O18 Orthorhombic and biaxial Mohs approximately 7–7.5 Violet-blue, blue-gray, and straw trichroism Cut orientation controls face-up color Iolite: Violet-Blue Cordierite, Three-Way Color, and the Geometry of Direction Iolite...
Dumortierite
Aluminum borosilicate Al7BO3(SiO4)3O3 Orthorhombic crystal system Mohs approximately 7–8.5 Fibrous blue to violet aggregates Dumortierite: Blue Fibers Shaped by Boron, Pressure, and Metamorphic Heat Dumortierite is a complex aluminum borosilicate...
Dumortierite
Aluminum borosilicate Al7BO3(SiO4)3O3 Orthorhombic crystal system Mohs approximately 7–8.5 Fibrous blue to violet aggregates Dumortierite: Blue Fibers Shaped by Boron, Pressure, and Metamorphic Heat Dumortierite is a complex aluminum borosilicate...
Heliotrope
Chalcedony variety Silicon dioxide, SiO2 Mohs 6.5–7 Deep green with red iron-oxide spots Traditional March birthstone Heliotrope Bloodstone: Deep Green Chalcedony Marked by Red Iron Heliotrope, widely known as bloodstone,...
Heliotrope
Chalcedony variety Silicon dioxide, SiO2 Mohs 6.5–7 Deep green with red iron-oxide spots Traditional March birthstone Heliotrope Bloodstone: Deep Green Chalcedony Marked by Red Iron Heliotrope, widely known as bloodstone,...