Pseudograndreefite is an extremely rare lead sulfate fluoride mineral found primarily in the oxidation zones of hydrothermal lead deposits. Collectors should look for its characteristic adamantine luster and tabular crystal habit in specimens from the Grand Reef Mine.

Hardness

~2.5

Mohs

Luster

Subadamantine

Streak

White

Transparency

Transparent

mineralrare

Pseudograndreefite

Hardness: ~2.5
Luster: Subadamantine
Streak: White
Transparency: Transparent

No image

Is this pseudograndreefite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch pseudograndreefite with a known reference. Pseudograndreefite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: subadamantine.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals.

Often confused with

Pseudograndreefite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Streak differs, so Pseudograndreefite leaves white, Linarite leaves pale blue; luster reads subadamantine on Pseudograndreefite and vitreous to subadamantine on Linarite.

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Often found alongside pseudograndreefite

Minerals reported to co-occur with pseudograndreefite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Pb₆SO₄F₁₀
Mohs hardness: ~2.5
Density: 7.0 g/cm³
Colors: Colorless
Streak: White
Luster: Subadamantine
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a vug isolated from acidic sulfate-rich solutions in the oxidized zone of a low-temperature Pb–Cu–Ag deposit

Where rockhounds find pseudograndreefite

Classic worldwide localities

Grand Reef mine, about six km northeast of Klondyke, Aravaipa district, Graham Co., Arizona, USA

Field-hunting tip

Where it forms: In a vug isolated from acidic sulfate-rich solutions in the oxidized zone of a low-temperature Pb–Cu–Ag deposit. If you start seeing grandreefite, 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

How do you identify pseudograndreefite?+

Mohs hardness is ~2.5. Luster: subadamantine. The streak is white. Common colors include colorless.

Where is pseudograndreefite found?+

Notable localities include Grand Reef mine, about six km northeast of Klondyke, Aravaipa district, Graham Co., Arizona, USA.

Is pseudograndreefite safe to handle?+

Pseudograndreefite contains lead. Contains lead, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling specimens.

What rocks look like pseudograndreefite?+

Pseudograndreefite is most often confused with Grandreefite, Linarite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with pseudograndreefite?+

Pseudograndreefite commonly co-occurs with Grandreefite, Laurelite, Aravaipaite, Galena, Fluorite, Anglesite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pseudograndreefite form in?+

Where it forms: In a vug isolated from acidic sulfate-rich solutions in the oxidized zone of a low-temperature Pb–Cu–Ag deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pseudograndreefite used for?+

Pseudograndreefite is used in collector.

Find pseudograndreefite on the map

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