mineral

Chalcedony Geode Fragment

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grayish-white to tan; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic; Cleavage: None; Conchoidal fracture; Specific gravity: 2.58–2.64.

Hardness: 6
Color: Grayish-white to tan
Luster: Waxy to vitreous

Identified April 20, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Grayish-white to tan; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic; Cleavage: None; Conchoidal fracture; Specific gravity: 2.58–2.64.

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. This specimen appears to be a small geode fragment showing a botryoidal or pocket-like formation.

Uses & applications

Used primarily for lapidary work, decorative specimens, jewelry (cabochons), and as a collector's item.

Geological facts

Chalcedony is composed of microscopic fibers of quartz and moganite. When found in nodules with hollow centers, they are termed geodes. Historically, it was used to create cylinder seals in Mesopotamia.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture (curved breaks), and hardness (it will scratch glass). Commonly found in desert regions, gravel beds, or volcanic ash deposits.

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