mineral
Botryoidal Quartz or Chalcedony
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed via precipitation of silica-rich hydrothermal fluids in cavities or fractures within volcanic or sedimentary rocks, often creating these 'bumpy' botryoidal (grape-like) textures.
Uses & applications
Used for lapidary work, jewelry making, and as decorative display specimens for mineral collectors.
Geological facts
The term 'botryoidal' comes from the Greek word 'botrys', meaning a bunch of grapes. This specific bubbly habit occurs when the mineral grows around many nuclei at once.
Field identification & locations
Identify in the field by its hardness (will scratch glass), grape-like surface texture, and lack of crystal faces. Commonly found in Arizona, Mexico, and volcanic regions globally.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock