sedimentary
Druzy Agate Geode
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs); Color: Grey, brown, and pinkish-red; Luster: Waxy to vitreous; Crystal Structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Grey, brown, and pinkish-red
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Grey, brown, and pinkish-red; Luster: Waxy to vitreous; Crystal Structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.64
Formation & geological history
Formed in cavities within volcanic or sedimentary rocks through the slow precipitation of silica-rich groundwater. Over time, layers of chalcedony form, sometimes leaving a central void where tiny 'druzy' quartz crystals grow. These can range from Tertiary to prehistoric ages.
Uses & applications
Primarily used for lapidary work, jewelry (pendants and beads), ornamental display, and as a collectible specimen for geological study.
Geological facts
The word 'druzy' refers to the glittering effect of tiny crystals on a rock surface. Agates are unique because no two patterns or vugs are exactly alike, often acting as a record of local mineral infusions like hematite or goethite which provide the red/pink colors seen here.
Field identification & locations
Identify in the field by looking for rounded, potato-like nodules with a rough exterior shell. When broken, they reveal distinct bands or crystalline centers. Common in the American West (Thunder Eggs), Brazil, and Morocco.
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