mineral

Banded Agate (Onyx type)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5–7 (Mohs scale); Color: Black with white/grey parallel banding; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Black with white/grey parallel banding
Luster: Vitreous to waxy

Identified February 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica-rich groundwater within cavities (vesicles) of igneous volcanic rocks, such as basalt or andesite, over thousands of years. The layers represent different pulses of mineralized hydrothermal fluids.

Uses & applications

Used primarily in lapidary work for jewelry (cabochons, beads), decorative carvings, and as a semi-precious gemstone in fashion accessories. In metaphysical circles, it is used as a protection or grounding stone.

Geological facts

While the note says 'quartz titane brut' (rough titanium quartz), this specific specimen is a polished tumbled agate. Natural black and white banded agate is often commercially called Onyx, though historically 'Onyx' refers specifically to parallel-banded varieties rather than chaotic bands.

Field identification & locations

Identify in the field by its distinct parallel banding, hardness (it will scratch glass), and smooth, waxy texture. Commonly found in Brazil, India, Madagascar, and the United States. It is a staple for beginner rock collectors due to its accessibility and beauty.