mineral

Chalcedony (Botryoidal or Geode form)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: White to light blue/grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: White to light blue/grey
Luster: Waxy to vitreous

Identified March 22, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: White to light blue/grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific Gravity: 2.58-2.64.

Formation & geological history

Formed through the low-temperature deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. This specimen likely originated as a small geode or nodule filling in basalt or limestone during the Cenozoic era or older.

Uses & applications

Used primarily in jewelry (cabochons, beads), ornamental carvings, and as a popular collector's specimen. In industry, it can be used as an abrasive or in precision bearings.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. The 'bubbly' texture seen in the specimen is known as a botryoidal habit, resembling a cluster of grapes.

Field identification & locations

Identify in the field by its waxy luster, lack of visible crystals, and extreme hardness (it will scratch glass). Commonly found in the Western US (e.g., Arizona, Oregon), Brazil, and Iceland. Collectors should look for unique banding or blue tints.

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