Rock Identifier
Yellow agate or yellow chalcedony bead strand (Microcrystalline quartz (SiO₂), chalcedony; possibly iron-stained agate or heat-treated quartz) — gemstone
gemstone

Yellow agate or yellow chalcedony bead strand

Microcrystalline quartz (SiO₂), chalcedony; possibly iron-stained agate or heat-treated quartz

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent honey-yellow to orange, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, and specific gravity about 2.60–2.65. Rounded polished beads show cloudy internal banding and inclusions.

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Physical properties

Mohs hardness 6.5–7; translucent honey-yellow to orange, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, and specific gravity about 2.60–2.65. Rounded polished beads show cloudy internal banding and inclusions.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly with iron producing the yellow color; agate formation spans many geological ages, often Cenozoic to older volcanic settings. Some commercial material may be dyed or heat-treated.

Uses & applications

Used for jewelry, beads, carvings, cabochons, and ornamental objects; durable but less valuable than transparent yellow gemstones such as citrine or golden beryl.

Geological facts

Agate is a variety of chalcedony distinguished by layered or patterned growth, while uniform material is generally called yellow chalcedony. Color and translucency can vary substantially within one strand.

Field identification & locations

Identify by its quartz-like hardness, cool feel, waxy luster, conchoidal fracture, and lack of cleavage; glass or plastic imitations are softer and may show bubbles. Common sources include Brazil, Uruguay, India, Madagascar, and Mexico.