Crystals
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,...
Diamond
Carbon mineral Chemical symbol C Isometric crystal system Mohs 10 Refractive index 2.417 Diamond: Carbon Lattice, Spectral Fire, and the Engineering of Light Diamond is carbon arranged in an exceptionally...
Diamond
Carbon mineral Chemical symbol C Isometric crystal system Mohs 10 Refractive index 2.417 Diamond: Carbon Lattice, Spectral Fire, and the Engineering of Light Diamond is carbon arranged in an exceptionally...
Granite
Felsic intrusive igneous rock Quartz + alkali feldspar + plagioclase Coarse interlocking crystals Commonly about 65–77% SiO2 Typical density about 2.6–2.75 g/cm³ Granite: The Crystalline Framework of Continents Granite is...
Granite
Felsic intrusive igneous rock Quartz + alkali feldspar + plagioclase Coarse interlocking crystals Commonly about 65–77% SiO2 Typical density about 2.6–2.75 g/cm³ Granite: The Crystalline Framework of Continents Granite is...