Grandreefite is a rare lead sulfate-fluoride mineral named after its type locality at the Grand Reef mine in Arizona. It typically forms clear, tabular, adamantine-luster crystals that are often found associated with other lead-bearing minerals in oxidized vein deposits.
Is this grandreefite?
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 grandreefite with a known reference. Grandreefite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: subadamantine.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Grandreefite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads subadamantine on Grandreefite and adamantine, resinous to vitreous on Anglesite.
How to tell apart: Luster reads subadamantine on Grandreefite and adamantine to resinous, pearly on cleavage surfaces on Lanarkite.
Often found alongside grandreefite
Minerals reported to co-occur with grandreefite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂SO₄F₂
- Mohs hardness
- ~2.5
- Density
- 7.0 g/cm³
- Colors
- Streak
- White
- Luster
- Subadamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in isolated vugs in the oxidized portions of a breccia-hosted hydrothermal Cu–Pb–Ag deposit
Where rockhounds find grandreefite
Classic worldwide localities
- Grand Reef mine, about six km northeast of Klondyke, Aravaipa district, Graham Co., Arizona, USA
Field-hunting tip
Where it forms: A rare secondary mineral in isolated vugs in the oxidized portions of a breccia-hosted hydrothermal Cu–Pb–Ag deposit. If you start seeing pseudograndreefite, laurelite, aravaipaite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find grandreefite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
