mineral

Chalcedony (Agate/Blue Quartzite)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grayish-blue, milky white with translucent patches; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific gravity: 2.6-2.64

Hardness: 6
Color: Grayish-blue, milky white with translucent patches
Luster: Waxy to vitreous

Identified March 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of igneous rocks or sedimentary layers over millions of years. This specimen shows water-worn tumbling, likely from a river or glacial deposit.

Uses & applications

Used primarily in lapidary arts, jewelry (cabochons), and as a decorative pocket stone. Historically used for making precision bearings and seals due to its toughness.

Geological facts

In many cultures, chalcedony was considered a stone of communication and peace. It lacks visible crystals because they are microscopic and fibrous, unlike macro-crystalline quartz.

Field identification & locations

Identify by its waxy surface and lack of visible grains. It cannot be scratched by a steel knife. Common in volcanic regions and riverbeds; collectors often find these in the Great Lakes region or Pacific Northwest.

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