Crystals
Sardonyx
Parallel-banded chalcedony SiO2 Sard red-brown layers with white, gray, or black onyx bands Polycrystalline quartz aggregate with variable moganite Mohs hardness about 6.5–7 Specific gravity commonly about 2.58–2.64 Waxy to...
Sardonyx
Parallel-banded chalcedony SiO2 Sard red-brown layers with white, gray, or black onyx bands Polycrystalline quartz aggregate with variable moganite Mohs hardness about 6.5–7 Specific gravity commonly about 2.58–2.64 Waxy to...
Sapphire
Gem variety of corundum Al2O3 All gem corundum outside the red ruby range Trigonal crystal system Mohs hardness 9 Specific gravity about 3.98–4.10 Uniaxial negative with directional color Metamorphic and...
Sapphire
Gem variety of corundum Al2O3 All gem corundum outside the red ruby range Trigonal crystal system Mohs hardness 9 Specific gravity about 3.98–4.10 Uniaxial negative with directional color Metamorphic and...
Tektite
Tektite • natural terrestrial glass launched from an impact site and deposited across a strewn field Formed during hypervelocity meteorite or asteroid impacts Amorphous glass • no crystal system or...
Tektite
Tektite • natural terrestrial glass launched from an impact site and deposited across a strewn field Formed during hypervelocity meteorite or asteroid impacts Amorphous glass • no crystal system or...
Stromatolite
Stromatolite • laminated microbialite built through repeated surface accretion Microbial mats trap, bind, stabilize, and mineralize sediment Planar, domal, columnar, branching, and conical forms Commonly carbonate; also silicified, dolomitized, phosphatic,...
Stromatolite
Stromatolite • laminated microbialite built through repeated surface accretion Microbial mats trap, bind, stabilize, and mineralize sediment Planar, domal, columnar, branching, and conical forms Commonly carbonate; also silicified, dolomitized, phosphatic,...
Shungite
Shungite • carbon-rich rock and natural solid carbonaceous matter No fixed mineral formula Onega Basin • Republic of Karelia Zaonega Formation • approximately 2.10–1.98 billion years old Disordered sp²-rich carbon...
Shungite
Shungite • carbon-rich rock and natural solid carbonaceous matter No fixed mineral formula Onega Basin • Republic of Karelia Zaonega Formation • approximately 2.10–1.98 billion years old Disordered sp²-rich carbon...
Shattuckite
Shattuckite • copper silicate hydroxide Formula: Cu5(SiO3)4(OH)2 Orthorhombic • fibrous, acicular, radial, felted, and massive Mohs about 3.5 • specific gravity about 3.8–4.1 Silky to dull luster • pale-blue streak...
Shattuckite
Shattuckite • copper silicate hydroxide Formula: Cu5(SiO3)4(OH)2 Orthorhombic • fibrous, acicular, radial, felted, and massive Mohs about 3.5 • specific gravity about 3.8–4.1 Silky to dull luster • pale-blue streak...