Matrix opal is a type of precious opal where the opal forms within the voids and fissures of the host rock, typically sandstone or ironstone. Collectors prize specimens that display vivid flashes of color (play-of-color) against a dark or earthy background matrix. Because the opal is intricately connected to the host, it is often cut and polished as a whole piece, sometimes treated to enhance the contrast of the color play.
Is this matrix opal?
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 matrix opal with a known reference. Matrix Opal sits at Mohs 5.5-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Matrix Opal leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Matrix Opal typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: multicolored, brown, black, gray.
- 5Look at form & habitCrystal system: amorphous. Typical habit: massive.
Often confused with
Matrix Opal vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside matrix opal
Minerals reported to co-occur with matrix opal. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂·nH₂O
- Mohs hardness
- 5.5-6.5
- Density
- 1.9-2.2 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Opaque
- Crystal system
- Amorphous
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Gemstone, Lapidary, Collector
- Host rock
- Sedimentary Sandstone or Ironstone Nodules
- Typical price
- $10-100 per piece depending on color play
Where rockhounds find matrix opal
Classic worldwide localities
- Andamooka, Australia
- Queensland, Australia
- Brazil
- Honduras
Field-hunting tip
Look in sedimentary sandstone or ironstone nodules country — that is the host setting where matrix opal typically forms. If you start seeing sandstone, ironstone, quartz in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify matrix opal?+
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Find matrix opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
