mineral

Carnelian (Agate)

SiO2 (Silicon Dioxide with Iron Oxide impurities)

Hardness: 6.5-7 on the Mohs scale. Color: Orange to reddish-brown (waxy translucent). Luster: Vitreous to waxy. Crystal structure: Trigonal/Microcrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.58–2.64.

Hardness: 6
Color: Orange to reddish-brown (waxy translucent)
Luster: Vitreous to waxy

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed in volcanic cavities or sedimentary rock where silica-rich groundwater deposits microcrystalline quartz layers. Its reddish color is derived from iron oxide (hematite) impurities throughout the formation process.

Uses & applications

Primarily used in jewelry (cabochons, beads), decorative lapidary arts, and as a collector's gemstone. Historically significant for intaglio seals and amulets.

Geological facts

In ancient Egypt, carnelian was known as the 'setting sun' and was used in the burial mask of Tutankhamun. It is often heat-treated commercially to enhance the red tones by oxidizing the iron content.

Field identification & locations

Identify by its waxy luster and translucency when held to light. It lacks the distinct banding of standard agate but often shares the same riverbed or beach environments. Common sources include Brazil, India, and the Pacific Northwest of the USA.

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