Decrespignyite-(Y) is a rare secondary mineral found primarily as tiny, vibrant blue to emerald-green platy crystals or crusts. It is most famous from the Mount Painter region in Australia, where it occurs within vugs of iron-rich host rocks. Its unique composition, involving both copper and yttrium, makes it a highly sought-after prize for advanced mineral collectors.
Is this decrespignyite-(y)?
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 decrespignyite-(y) with a known reference. Decrespignyite-(Y) sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Decrespignyite-(Y) leaves a pale blue streak.
- 3Read the lusterHold the specimen under a strong light. Decrespignyite-(Y) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, greenish-blue, emerald-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, rosettes.
Often confused with
Decrespignyite-(Y) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Decrespignyite-(Y) leaves pale blue, Malachite leaves light green.
How to tell apart: Streak differs — Decrespignyite-(Y) leaves pale blue, Azurite leaves light blue; luster reads vitreous on Decrespignyite-(Y) and vitreous to dull on Azurite.
How to tell apart: Decrespignyite-(Y) is noticeably harder (Mohs 3 vs. 2); luster reads vitreous on Decrespignyite-(Y) and pearly on Aurichalcite.
Often found alongside decrespignyite-(y)
Minerals reported to co-occur with decrespignyite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Cu,Y,REE)₄(CO₃)₂(OH)₆·2H₂O
- Mohs hardness
- 3
- Density
- 3.5 g/cm³
- Streak
- Pale Blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Rosettes
- Cleavage
- None Observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Brecciated Hematite-rich Rocks
- Typical price
- $100-500 per specimen
Where rockhounds find decrespignyite-(y)
Classic worldwide localities
- Mount Painter, South Australia, Australia
Field-hunting tip
Look in hydrothermal veins in brecciated hematite-rich rocks country — that is the host setting where decrespignyite-(y) typically forms. If you start seeing malachite, azurite, brochantite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, rosettes habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify decrespignyite-(y)?+
Where is decrespignyite-(y) found?+
How much is decrespignyite-(y) worth?+
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What rocks look like decrespignyite-(y)?+
What minerals are found with decrespignyite-(y)?+
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Find decrespignyite-(y) on the map
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