Ignimbrite is a hard, indurated volcanic rock formed by the deposition of pyroclastic flows from explosive eruptions. Collectors often look for the distinct eutaxitic or flow-banded textures resulting from the compaction and welding of hot glass shards and pumice fragments.
Is this ignimbrite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch ignimbrite with a known reference. Ignimbrite sits at Mohs 5-7, softer than the next harder reference, harder than the previous one.
- 2Read the textureLook at a fresh break with a hand lens. Texture: Typically welded tuff; very poorly sorted.
- 3Pick out the mineralsComposition: Volcanic ash of glass shards and crystal fragments, with pumice or scoria lapilli and lithic fragments. Identify the two or three most abundant grains.
- 4Read the lusterHold the specimen under a strong light. Luster: dull.
- 5Match the color rangeCompare against the expected color range: gray, white, pink, brown, black.
Often confused with
Ignimbrite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ignimbrite
Minerals reported to co-occur with ignimbrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 5-7
- Density
- 2.3-2.6 g/cm³
- Luster
- Dull
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Decorative, Building material, Collector
- Host rock
- volcanic centers
- Texture
- Typically welded tuff; very poorly sorted
- Composition
- Volcanic ash of glass shards and crystal fragments, with pumice or scoria lapilli and lithic fragments
Where rockhounds find ignimbrite
Classic worldwide localities
- New Zealand
- Greece
- USA (Nevada, Idaho)
- Italy
- Peru
Field-hunting tip
Where it forms: volcanic centers. If you start seeing quartz, sanidine, plagioclase in float, you are in the right ground.
Common questions
How do you identify ignimbrite?+
Where is ignimbrite found?+
What rocks look like ignimbrite?+
What minerals are found with ignimbrite?+
What kind of rock does ignimbrite form in?+
What is ignimbrite used for?+
Find ignimbrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
