mineral
Green agate/geode slab
Cryptocrystalline quartz (chalcedony), SiO₂, likely agate with druzy quartz
AI-generated identification · may be incorrectTranslucent blue-green to olive-gray chalcedony with waxy luster, irregular conchoidal fracture, and a rough tan-brown host rind; hardness about 6.5–7 Mohs, no cleavage, specific gravity approximately 2.6. The cavity appears lined with fine crystalline quartz or chalcedony.
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Physical properties
Translucent blue-green to olive-gray chalcedony with waxy luster, irregular conchoidal fracture, and a rough tan-brown host rind; hardness about 6.5–7 Mohs, no cleavage, specific gravity approximately 2.6. The cavity appears lined with fine crystalline quartz or chalcedony.
Formation & geological history
Formed when silica-rich groundwater filled cavities in volcanic rock, depositing chalcedony in layers and later quartz crystals in the open void. Such agates are typically Cenozoic to older volcanic-hosted deposits, though the exact age and locality cannot be determined from the image.
Uses & applications
Cut and polished for decorative slabs, bookends, carvings, and jewelry; attractive pieces are popular among collectors. Rough material is also used for cabochons and lapidary art.
Geological facts
The banded or translucent body is characteristic of agate, a variety of chalcedony. Green coloration may result from chlorite, celadonite, iron minerals, or artificial dyeing; testing is needed to distinguish natural color.
Field identification & locations
Common in volcanic terrains worldwide, especially Brazil, Uruguay, Mexico, Madagascar, India, and the western United States. Look for translucency, waxy chalcedony, curved fracture, and a contrasting volcanic rind.
