Rock Identifier
Botryoidal Chalcedony with Iron Staining (Microcrystalline Quartz (SiO2)) — mineral
mineral

Botryoidal Chalcedony with Iron Staining

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Translucent white to tan with orange/brown iron oxide staining. Luster: Waxy to vitreous. Structure: Botryoidal (grape-like) or druzy surface. No cleavage. Specific gravity: 2.6-2.65.

Hardness
6
Luster
Waxy to vitreous
Identified More mineral
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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Translucent white to tan with orange/brown iron oxide staining. Luster: Waxy to vitreous. Structure: Botryoidal (grape-like) or druzy surface. No cleavage. Specific gravity: 2.6-2.65.

Formation & geological history

Formed from the deposition of silica-rich hydrothermal fluids in cavities of volcanic or sedimentary rocks. The orange coloration is due to the presence of limonite or hematite during or after formation.

Uses & applications

Used as decorative display pieces, tumbled stones for metaphysical use, and occasionally carved into jewelry or cabochons.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. When it forms in small rounded bumps, it is called 'botryoidal' from the Greek word for a bunch of grapes.

Field identification & locations

Identify by its characteristic 'bubbly' or rounded surface texture, waxy luster, and its ability to scratch glass. Commonly found in desert regions, riverbeds, and volcanic areas in the Western United States, Brazil, and India.