Appearance: • Chalcedony is microcrystalline or cryptocrystalline quartz; hexagonal (trigonal) crystal system; chemical composition SiO2• Semitransparent Identification: • Optic Character: AGG• Refractive Index: 1.535-1.539; 1.53 or 1.54 spot reading• Birefringence: usually not detectable, but may show .004• Pleochroism: none• Ultraviolet Fluorescence: generally inert (LW and SW); some may fluoresce a yellowish green (LW and SW)• […]
Appearance: • Chalcedony is microcrystalline or cryptocrystalline quartz; hexagonal (trigonal) crystal system; chemical composition SiO2• semitransparent Identification: • Optic Character: AGG• Refractive Index: 1.535-1.539; 1.53 or 1.54 spot reading• Birefringence: usually not detectable, but may show .004• Pleochroism: none• Ultraviolet Fluorescence: generally inert (LW and SW); some may fluoresce a yellowish green (LW and SW)• […]
Appearance: • Chalcedony (kal-SED-uh-nee) is microcrystalline or cryptocrystalline quartz; hexagonal (trigonal) crystal system; chemical composition SiO2• Semitransparent to opaque• Black, no banded, some with dyed treatment from natural grey agate Identification: • Optic Character: AGG• Refractive Index: 1.535-1.539; 1.53 or 1.54 spot reading• Birefringence: usually not detectable, but may show .004• Pleochroism: none• Ultraviolet Fluorescence: […]
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