Tube Agate is a variety of chalcedony characterized by distinctive, hollow, tube-like formations that often radiate within the stone. These tubes, which can be clear or filled with contrasting minerals, are created during the deposition process in volcanic cavities. Collectors prize them for their unique structural patterns which reveal intricate details when sliced and polished.

Hardness

6.5-7

Mohs

Luster

Waxy

Streak

White

Transparency

Translucent

mineralcommonQuartz family

Tube Agate

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

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Is this tube agate?

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 tube agate with a known reference. Tube Agate 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. Tube Agate leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Tube Agate typically shows a waxy luster.
4
Match the color range
Compare against the expected color range: white, gray, blue, yellow, brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: botryoidal.

Often confused with

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

Often found alongside tube agate

Minerals reported to co-occur with tube agate. 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: 2.6-2.7 g/cm³
Colors: White Gray Blue Yellow Brown
Streak: White
Luster: Waxy
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Botryoidal
Cleavage: None
Rarity: Common
Uses: Lapidary, Collector, Decorative
Host rock: Rhyolite Cavities
Typical price: $5-50 thumbnail, $50-200 cabinet specimen

Where rockhounds find tube agate

Classic worldwide localities

Ojo Laguna, Mexico
Montana, USA
Agua Nueva, Mexico
Patagonia, Argentina

Field-hunting tip

Look in rhyolite cavities country — that is the host setting where tube agate typically forms. If you start seeing quartz, calcite, goethite in float, you are in the right ground. Field specimens usually show a botryoidal habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tube agate?+

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

Where is tube agate found?+

Notable localities include Ojo Laguna, Mexico; Montana, USA; Agua Nueva, Mexico; Patagonia, Argentina.

How much is tube agate worth?+

Typical asking prices fall in the range of $5-50 thumbnail, $50-200 cabinet specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like tube agate?+

Tube Agate is most often confused with Chalcedony. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tube agate?+

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

What kind of rock does tube agate form in?+

Tube Agate typically forms in rhyolite cavities. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tube agate used for?+

Tube Agate is used in lapidary, collector, decorative.

Find tube agate on the map

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