Rock Identifier
Banded Agate (Onyx type) (Silicon Dioxide (SiO2) - Cryptocrystalline Quartz) — mineral
mineral

Banded Agate (Onyx type)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

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 More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App StoreGoogle Play

Physical properties

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.

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.

More like this

Other mineral specimens

Sandstone (with potential mineral staining/concretions) (Arenite (SiO2 based)) — sedimentary

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary
Epidote (Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)) — metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic
Nephrite Jade (Nephrite) — Mineral/Rock

Nephrite Jade

Nephrite

Mineral/Rock
Banded Gneiss (River Rock/Pebble) (Gneiss (specifically a banded variety often found as a river rock)) — Metamorphic Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock
Green Apatite on Albite (Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]) — mineral

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral
Epidote (Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)) — mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral