Perloffite is a rare phosphate mineral primarily found in complex granite pegmatites. It typically appears as dark brown, tabular, or blocky crystals and is highly sought after by advanced systematic mineral collectors.

Hardness

Mohs

Luster

Vitreous to subadamantine

Streak

Greenish yellow

Transparency

Semitransparent

mineralrareBjarebyite Group family

Perloffite

Hardness: ~5
Luster: Vitreous to subadamantine
Streak: Greenish yellow
Transparency: Semitransparent

Is this perloffite?

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 perloffite with a known reference. Perloffite sits at Mohs ~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: greenish yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to subadamantine.
4
Match the color range
Compare against the expected color range: dark brown, brownish black, greenish brown, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: spear head.

Often confused with

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

mineral

Bjarebyite

Mohs 4

How to tell apart: Perloffite is noticeably harder (Mohs ~5 vs. 4); streak differs, so Perloffite leaves greenish yellow, Bjarebyite leaves white; luster reads vitreous to subadamantine on Perloffite and subadamantine on Bjarebyite.

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Often found alongside perloffite

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

All properties

Chemical formula: BaMn²⁺₂Fe³⁺₂(PO₄)₃(OH)₃
Mohs hardness: ~5
Density: 3.32 g/cm³
Colors: Dark brown Brownish black Greenish brown Black
Streak: Greenish yellow
Luster: Vitreous to subadamantine
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Spear head
Cleavage: On {100}, perfect
Rarity: Rare
Uses: Collector
Host rock: A rare secondary mineral in a complex zoned granite pegmatite (Big Chief mine, South Dakota, USA)

Where rockhounds find perloffite

Classic worldwide localities

Big Chief mine, one km south of Glendale, Pennington Co., South Dakota, USA
Spring Creek copper mine, near Wilmington, South Australia
Hagendorf, Bavaria, Germany

Field-hunting tip

Where it forms: A rare secondary mineral in a complex zoned granite pegmatite (Big Chief mine, South Dakota, USA). If you start seeing ludlamite, huréaulite, siderite in float, you are in the right ground. Typical habit: spear head. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify perloffite?+

Mohs hardness is ~5. Luster: vitreous to subadamantine. The streak is greenish yellow. Common colors include dark brown, brownish black, greenish brown, black.

Where is perloffite found?+

Notable localities include Big Chief mine, one km south of Glendale, Pennington Co., South Dakota, USA; Spring Creek copper mine, near Wilmington, South Australia; Hagendorf, Bavaria, Germany.

What rocks look like perloffite?+

Perloffite is most often confused with Bjarebyite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with perloffite?+

Perloffite commonly co-occurs with Ludlamite, Huréaulite, Siderite, Triphylite, Barite, Copper. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does perloffite form in?+

Where it forms: A rare secondary mineral in a complex zoned granite pegmatite (Big Chief mine, South Dakota, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is perloffite used for?+

Perloffite is used in collector.

Find perloffite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.