Onyx is a variety of chalcedony characterized by parallel, straight bands of different colors, most famously black and white. It is typically found in volcanic cavities and is widely used for cameos and decorative objects due to its ability to take a high polish.

Hardness

6.5-7

Mohs

Luster

Waxy

Streak

White

Transparency

Translucent

mineralcommonChalcedony family

Onyx

Hardness: 6.5-7
Luster: Waxy
Streak: White
Transparency: Translucent

Is this onyx?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch onyx with a known reference. Onyx sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Onyx leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Onyx typically shows a waxy luster.
4
Match the color range
Compare against the expected color range: black, white, banded.
5
Look at form & habit
Crystal system: trigonal. Typical habit: massive.

Often confused with

Onyx vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Luster reads waxy on Onyx and vitreous on Obsidian.

Compare →

Often found alongside onyx

Minerals reported to co-occur with onyx. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: SiO₂
Mohs hardness: 6.5-7
Density: 2.6-2.65 g/cm³
Colors: Black White Banded
Streak: White
Luster: Waxy
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Massive
Cleavage: None
Rarity: Common
Uses: Lapidary, Ornamental, Jewelry
Host rock: Hydrothermal Veins, Amygdaloidal Cavities in Basalt
Typical price: $5-50 for small polished pieces or decorative carvings

Where rockhounds find onyx

14 mapped spots

Classic worldwide localities

Brazil
India
Uruguay
Pakistan
USA

Field-hunting tip

Look in hydrothermal veins, amygdaloidal cavities in basalt country — that is the host setting where onyx typically forms. If you start seeing quartz, calcite, agate in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico, Utah, Montana — start trip planning there.

Browse 14 U.S. spots for onyx →

Common questions

How do you identify onyx?+

Mohs hardness is 6.5-7. It typically shows a waxy luster. The streak is white. Common colors include black, white, banded.

Where is onyx found?+

Notable localities include Brazil; India; Uruguay; Pakistan; USA.

Can I find onyx in the United States?+

RockHoundR maps 14 onyx rockhounding spots across 7 U.S. states — the top states are New Mexico, Utah, Montana.

How much is onyx worth?+

Typical asking prices fall in the range of $5-50 for small polished pieces or decorative carvings. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like onyx?+

Onyx is most often confused with Sard, Black Agate, Obsidian. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with onyx?+

Onyx commonly co-occurs with Quartz, Calcite, Agate. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does onyx form in?+

Onyx typically forms in hydrothermal veins, amygdaloidal cavities in basalt. Working float back to the host body is the standard way to chase a fresh occurrence.

What is onyx used for?+

Onyx is used in lapidary, ornamental, jewelry.

Find onyx on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.