Grape Agate Specimen (Indonesia)

Mounted in a small display box with a label bearing the mineral name, chemical formula, and origin.

Geologic Information & History

Technically not an agate at all, grape agate is a botryoidal form of amethystine quartz (SiO₂). The purple coloration is caused by iron (Fe) atoms trapped in the crystal structure, while the green is caused by the inclusion of other minerals (possibly celadonite [K(Si₄O₁₀)], a type of mica).

Dimensions & Specifications

Specific Gravity: 2.58-2.64
Hardness: 6.5-7
Material: Microcrystalline Quartz (var. Grape Agate) [SiO2]
Origin: Indonesia