sedimentary
Agate Geode with Quartz Druzy
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7.0 (Mohs scale), Color: Banded white, tan, and grey with a clear druzy center, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.64
- Hardness
- 6
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Physical properties
Hardness: 6.5-7.0 (Mohs scale), Color: Banded white, tan, and grey with a clear druzy center, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.64
Formation & geological history
Formed through the deposition of silica from groundwater in cavities (vesicles) within igneous or sedimentary rocks. Over millions of years, layers of chalcedony deposit along the walls, eventually forming the internal druzy crystals.
Uses & applications
Used primarily in lapidary arts, jewelry (cabochons), interior decor as bookends or display pieces, and collected by mineral enthusiasts.
Geological facts
Agate is named after the Achates River (now the Dirillo River) in Sicily. Geodes are unique because they are hollow, often holding well-formed crystals that were protected from environmental wear for millions of years.
Field identification & locations
Identify in the field by looking for nodular, rounded rocks with a rough, 'cauliflower-like' exterior. Often found in volcanic regions or limestone beds. Brazil and Uruguay are top producers of high-quality quartz-lined agates.
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