An obsidian nodule, often called an Apache tear, is a naturally rounded, pebble-like mass of volcanic glass. It is typically found embedded in a softer perlite matrix and is prized for its smooth, water-worn appearance and conchoidal fracture.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralcommonObsidian family

Obsidian Nodule

Hardness: 5-5.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this obsidian nodule?

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 obsidian nodule with a known reference. Obsidian Nodule sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: black, brown, gray.
5
Look at form & habit
Typical habit: rounded nodules.

Often confused with

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

How to tell apart: Schorl is the harder of the two (Mohs 7 vs. 5-5.5).

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Often found alongside obsidian nodule

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

All properties

Mohs hardness: 5-5.5
Density: 2.4 g/cm³
Colors: Black Brown Gray
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal habit: Rounded nodules
Cleavage: None
Rarity: Common
Uses: Lapidary, Collector, Decorative
Host rock: rhyolitic volcanic ash and perlite

Where rockhounds find obsidian nodule

Classic worldwide localities

Arizona, USA
Nevada, USA
Mexico
Iceland

Field-hunting tip

Where it forms: rhyolitic volcanic ash and perlite. If you start seeing perlite, rhyolite, quartz in float, you are in the right ground. Typical habit: rounded nodules. Train your eye for that shape before scanning the outcrop.

More obsidian nodule photos

Common questions

How do you identify obsidian nodule?+

Mohs hardness is 5-5.5. Luster: vitreous. The streak is white. Common colors include black, brown, gray.

Where is obsidian nodule found?+

Notable localities include Arizona, USA; Nevada, USA; Mexico; Iceland.

What rocks look like obsidian nodule?+

Obsidian Nodule is most often confused with Tektite, Schorl. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with obsidian nodule?+

Obsidian Nodule commonly co-occurs with Perlite, Rhyolite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does obsidian nodule form in?+

Where it forms: rhyolitic volcanic ash and perlite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is obsidian nodule used for?+

Obsidian Nodule is used in lapidary, collector, decorative.

Find obsidian nodule on the map

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