mineral

Agate Geode Slice with Druzy Quartz

Silicon Dioxide (SiO2) - Banded Chalcedony with Quartz

Hardness: 6.5-7 on Mohs scale. Luster: Waxy to vitreous. Color: Light blue-grey microcrystalline chalcedony core with small sparkling quartz druzy crystals and a dark green celadonite/basaltic outer rind. Structure: Trigonal/Hexagonal microcrystalline silica. Cleavage: None (conchoidal fracture).…

Hardness: 6
Luster: Waxy to vitreous

Identified July 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed in gas cavities (vesicles) within volcanic basaltic lava flows. Silica-rich hydrothermal fluids percolate through the rock, depositing layers of chalcedony over time, often ending with small crystalline quartz druzy in the central cavity.

Uses & applications

Popular for lapidary work, jewelry making, home decor display, polished coasters, and crystal collecting.

Geological facts

Agate geodes often contain a dark green outer rind composed of celadonite or chlorite minerals that coated the basalt cavity walls before silica deposition began.

Field identification & locations

Identified by concentric banding, translucent chalcedony layer, dark volcanic rind, and central pocket of tiny sparkling druzy quartz crystals. Widely found in Brazil, Uruguay, Madagascar, and the USA.

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