mineral
Agate (Chalcedony Nodule)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Translucent white to pale grey, yellowish, with iron staining and greenish/chloritic inclusions; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Translucent white to pale grey, yellowish, with iron staining and greenish/chloritic inclusions; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the deposition of silica-rich solutions in cavities or vesicles within volcanic or sedimentary rocks over millions of years.
Uses & applications
Lapidary projects, tumbling, cabochons, decorative ornaments, and collector specimens.
Geological facts
Agate is a cryptocrystalline variety of quartz characterized by its fine grain and brightness of color. Water-worn nodules like this often hide internal banding or moss-like inclusions visible when cut or polished.
Field identification & locations
Look for a translucent, waxy exterior, rounded water-worn smooth rind, and conchoidal fracture surfaces. Commonly found in riverbeds, beach gravels, and volcanic gravels worldwide.
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