Dessauite-(Y) is an extremely rare member of the crichtonite group, typically black to ash-gray. It occurs as tabular crystals in calcite veins cutting dolomite. It was first described from the Buca della Vena mine, Apuan Alps, Tuscany, Italy. Always handle with care due to its uranium content.
Is this dessauite-(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 dessauite-(y) with a known reference. Dessauite-(Y) sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: deep blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals.
Often confused with
Dessauite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Crichtonite is the harder of the two (Mohs 4.5-5 vs. 2.5); streak differs, so Dessauite-(Y) leaves pale blue, Crichtonite leaves dark gray; luster reads adamantine, pearly on cleavages on Dessauite-(Y) and metallic, dull to bright on Crichtonite.
How to tell apart: Lindsleyite is the harder of the two (Mohs 7.5 vs. 2.5); streak differs, so Dessauite-(Y) leaves pale blue, Lindsleyite leaves gray; luster reads adamantine, pearly on cleavages on Dessauite-(Y) and metallic on Lindsleyite.
How to tell apart: Mathiasite is the harder of the two (Mohs 7.5 vs. 2.5); streak differs, so Dessauite-(Y) leaves pale blue, Mathiasite leaves gray; luster reads adamantine, pearly on cleavages on Dessauite-(Y) and metallic on Mathiasite.
Often found alongside dessauite-(y)
Minerals reported to co-occur with dessauite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sr(Y,U,Mn)Fe₂(Ti,Fe,Cr,V)₁₈(O,OH)₃₈
- Mohs hardness
- 2.5
- Density
- 5.42 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Adamantine, pearly on cleavages
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular crystals
- Cleavage
- {001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In oxidized manganese ores (Mendip Hills, England); a secondary mineral in deeply oxidized Pb–Cu ores (Tiger, Arizona, USA); in slag exposed to seawater
Where rockhounds find dessauite-(y)
Classic worldwide localities
- Mammoth-St. Anthony mine, Tiger, Pinal Co., and from the Rowley mine, Maricopa Co., Arizona, USA
- Higher Pitts Farm, Mendip Hills, and the Merehead quarry, near Shepton Mallet, Somerset, England
- Padstow Consols, Padstow, Cornwall, England
- Christian-Levin mine, near Essen, North Rhine-Westphalia, and from Richelsdorf, Hesse, in slag, Germany
- Baratti Beach, Tuscany, Italy, in slag
- Laurium, Greece, in slag
Field-hunting tip
Where it forms: In oxidized manganese ores (Mendip Hills, England); a secondary mineral in deeply oxidized Pb–Cu ores (Tiger, Arizona, USA); in slag exposed to seawater. If you start seeing chloroxiphite, hydrocerussite, mendipite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify dessauite-(y)?+
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Is dessauite-(y) safe to handle?+
What rocks look like dessauite-(y)?+
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Find dessauite-(y) on the map
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