Crystals
Ruby with fuchsite
Ruby in Fuchsite • natural metamorphic rock containing corundum in chromium-rich mica Ruby: Al2O3 with Cr3+ Fuchsite: idealized K(Al,Cr)2(AlSi3O10)(OH)2 Common associate: blue or blue-green kyanite Possible matrix phases: quartz, feldspar,...
Ruby with fuchsite
Ruby in Fuchsite • natural metamorphic rock containing corundum in chromium-rich mica Ruby: Al2O3 with Cr3+ Fuchsite: idealized K(Al,Cr)2(AlSi3O10)(OH)2 Common associate: blue or blue-green kyanite Possible matrix phases: quartz, feldspar,...
Agate geode
Chalcedony rind Quartz druzy interior SiO2 Mohs 6.5–7 Cavity-grown crystals Agate Geodes: Banded Stone Cavities, Quartz Druzy, and Hidden Crystal Architecture Agate geodes are natural cavities lined first with chalcedony...
Agate geode
Chalcedony rind Quartz druzy interior SiO2 Mohs 6.5–7 Cavity-grown crystals Agate Geodes: Banded Stone Cavities, Quartz Druzy, and Hidden Crystal Architecture Agate geodes are natural cavities lined first with chalcedony...
Seraphinite
Seraphinite • lapidary trade name for plume-patterned clinochlore Representative clinochlore formula: Mg5Al(AlSi3O10)(OH)8 Chlorite group • layered phyllosilicate Monoclinic • perfect basal cleavage Silvery plumes from aligned reflective lamellae Mohs about...
Seraphinite
Seraphinite • lapidary trade name for plume-patterned clinochlore Representative clinochlore formula: Mg5Al(AlSi3O10)(OH)8 Chlorite group • layered phyllosilicate Monoclinic • perfect basal cleavage Silvery plumes from aligned reflective lamellae Mohs about...
Turquoise
Turquoise • hydrated copper–aluminum phosphate CuAl6(PO4)4(OH)8·4H2O Triclinic • commonly compact, microcrystalline, and vein-forming Mohs about 5–6 • lower in porous or altered material Blue, blue-green, green, and yellow-green Copper supplies...
Turquoise
Turquoise • hydrated copper–aluminum phosphate CuAl6(PO4)4(OH)8·4H2O Triclinic • commonly compact, microcrystalline, and vein-forming Mohs about 5–6 • lower in porous or altered material Blue, blue-green, green, and yellow-green Copper supplies...
Tourmaline
Tourmaline supergroup • boron-bearing ring silicates XY3Z6(T6O18)(BO3)3V3W Trigonal • polar and commonly hemimorphic Long striated prisms • rounded-triangular cross sections Mohs 7–7.5 • specific gravity about 2.82–3.32 Strong pleochroism •...
Tourmaline
Tourmaline supergroup • boron-bearing ring silicates XY3Z6(T6O18)(BO3)3V3W Trigonal • polar and commonly hemimorphic Long striated prisms • rounded-triangular cross sections Mohs 7–7.5 • specific gravity about 2.82–3.32 Strong pleochroism •...
Flint
Dark variety of chert Predominantly SiO2 Microcrystalline silica rock Mohs approximately 6.5–7 Conchoidal fracture Nodules and layers in chalk or limestone Produces sparks against high-carbon steel Black, gray, brown, honey,...
Flint
Dark variety of chert Predominantly SiO2 Microcrystalline silica rock Mohs approximately 6.5–7 Conchoidal fracture Nodules and layers in chalk or limestone Produces sparks against high-carbon steel Black, gray, brown, honey,...