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

Also: Apache Tear

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. Obsidian Nodule leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Obsidian Nodule typically shows a vitreous luster.
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 7-7.5 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

Look in rhyolitic volcanic ash and perlite country, the host setting where obsidian nodule typically forms. If you start seeing perlite, rhyolite, quartz in float, you are in the right ground. Field specimens usually show a rounded nodules habit, so 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. It typically shows a vitreous luster. 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?+

Obsidian Nodule typically forms in 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.