Chalcedony is a cryptocrystalline form of silica that typically forms in rounded, waxy masses or botryoidal crusts within volcanic vugs. Rockhounders often look for its distinctive waxy luster and conchoidal fracture, making it a favorite material for cabochons and lapidary work.

Hardness

6.5-7

Mohs

Luster

Waxy

Streak

White

Transparency

Translucent

mineralcommonQuartz family

Chalcedony

Also: white agate

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

Is this chalcedony?

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 chalcedony with a known reference. Chalcedony 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. Chalcedony leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Chalcedony typically shows a waxy luster.
4
Match the color range
Compare against the expected color range: white, gray, blue, brown, tan.
5
Look at form & habit
Crystal system: trigonal. Typical habit: botryoidal, massive, crusts, stalactitic.

Often confused with

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

mineral

Opalite

Mohs 5.5-6.5

How to tell apart: Luster reads waxy on Chalcedony and vitreous on Opalite.

Often found alongside chalcedony

Minerals reported to co-occur with chalcedony. 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: 2.58-2.64 g/cm³
Colors: White Gray Blue Brown Tan
Streak: White
Luster: Waxy
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Botryoidal, Massive, Crusts, Stalactitic
Cleavage: None
Rarity: Common
Uses: Lapidary, Decorative, Collector
Host rock: Volcanic Cavities, Hydrothermal Veins, Sedimentary Nodules

Where rockhounds find chalcedony

301 mapped spots

Classic worldwide localities

Brazil
India
Madagascar
USA
Mexico

U.S. states with chalcedony

Each link opens a state-specific list of mapped rockhounding spots that produce chalcedony.

Field-hunting tip

Look in volcanic cavities, hydrothermal veins, sedimentary nodules country, the host setting where chalcedony typically forms. If you start seeing quartz, calcite, zeolites in float, you are in the right ground. Field specimens usually show a botryoidal, massive, crusts, stalactitic habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Oregon, Wyoming. Start trip planning there.

Browse 301 U.S. spots for chalcedony →

Common questions

How do you identify chalcedony?+

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

Where is chalcedony found?+

Notable localities include Brazil; India; Madagascar; USA; Mexico.

Can I find chalcedony in the United States?+

RockHoundR maps 301 chalcedony rockhounding spots across 12 U.S. states. The top states are Utah, Oregon, Wyoming.

What rocks look like chalcedony?+

Chalcedony is most often confused with Opalite, Flint Nodule, Jasper. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with chalcedony?+

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

What kind of rock does chalcedony form in?+

Chalcedony typically forms in volcanic cavities, hydrothermal veins, sedimentary nodules. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chalcedony used for?+

Chalcedony is used in lapidary, decorative, collector.

Find chalcedony on the map

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