Crystals
Emerald
Green variety of beryl Be3Al2Si6O18 Hexagonal crystal system Mohs approximately 7.5–8 Chromium and/or vanadium color Jardin inclusions and fissures Rare six-spoked trapiche growth Clarity enhancement commonly disclosed Emerald: The Green...
Emerald
Green variety of beryl Be3Al2Si6O18 Hexagonal crystal system Mohs approximately 7.5–8 Chromium and/or vanadium color Jardin inclusions and fissures Rare six-spoked trapiche growth Clarity enhancement commonly disclosed Emerald: The Green...
Copper
Native-element metal Cu Atomic number 29 Isometric crystal system Face-centered cubic structure Mohs approximately 2.5–3 Specific gravity approximately 8.96 Brown, black, green, and blue patinas Natural copper–silver intergrowths Commonly associated...
Copper
Native-element metal Cu Atomic number 29 Isometric crystal system Face-centered cubic structure Mohs approximately 2.5–3 Specific gravity approximately 8.96 Brown, black, green, and blue patinas Natural copper–silver intergrowths Commonly associated...
Amber
Fossil resin Organic gem rather than a mineral Amorphous polymeric material Mohs approximately 2–2.5 Specific gravity approximately 1.05–1.10 Plant, fungal, and arthropod inclusions Variable fluorescence Natural, heated, clarified, pressed, or...
Amber
Fossil resin Organic gem rather than a mineral Amorphous polymeric material Mohs approximately 2–2.5 Specific gravity approximately 1.05–1.10 Plant, fungal, and arthropod inclusions Variable fluorescence Natural, heated, clarified, pressed, or...
Onyx
Banded chalcedony SiO2 Parallel black-and-white layers Sardonyx: brown-red and pale bands Mohs approximately 6.5–7 Waxy to vitreous luster Classic cameo and intaglio material Commercial black material is often treated Distinct...
Onyx
Banded chalcedony SiO2 Parallel black-and-white layers Sardonyx: brown-red and pale bands Mohs approximately 6.5–7 Waxy to vitreous luster Classic cameo and intaglio material Commercial black material is often treated Distinct...
Opal
Hydrated silica mineraloid SiO2·nH2O Amorphous to poorly ordered structure Mohs approximately 5–6.5 Play-of-color by diffraction Fire opal may be precious or common Hydrophane varieties absorb water Solid, boulder, matrix, doublet,...
Opal
Hydrated silica mineraloid SiO2·nH2O Amorphous to poorly ordered structure Mohs approximately 5–6.5 Play-of-color by diffraction Fire opal may be precious or common Hydrophane varieties absorb water Solid, boulder, matrix, doublet,...
Moqui
Iron-oxide sandstone concretions Hematite Fe2O3 Goethite FeO(OH) Quartz-sandstone interiors Navajo Sandstone host Groundwater and redox formation Usually weakly magnetic or nonmagnetic Earth analog for Martian spherules Moqui Marbles: Iron Concretions...
Moqui
Iron-oxide sandstone concretions Hematite Fe2O3 Goethite FeO(OH) Quartz-sandstone interiors Navajo Sandstone host Groundwater and redox formation Usually weakly magnetic or nonmagnetic Earth analog for Martian spherules Moqui Marbles: Iron Concretions...