Gatehouseite is an extremely rare manganese phosphate mineral found in complex granite pegmatites. It typically forms attractive, orange, bladed crystals in radial aggregates that are highly sought after by systematic mineral collectors.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

Yellowish

Transparency

Translucent

mineralrare

Gatehouseite

Hardness: 3-4
Luster: Vitreous
Streak: Yellowish
Transparency: Translucent

Is this gatehouseite?

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 gatehouseite with a known reference. Gatehouseite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Gatehouseite leaves a yellowish streak.
3
Read the luster
Hold the specimen under a strong light. Gatehouseite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: orange, brownish-orange.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: bladed crystals, radial sprays.

Often confused with

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

mineral

Fairfieldite

Mohs 3.5

How to tell apart: Streak differs — Gatehouseite leaves yellowish, Fairfieldite leaves white.

Compare →

Often found alongside gatehouseite

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

All properties

Chemical formula: Mn₅(PO₄)₂(OH)₄
Mohs hardness: 3-4
Density: 3.32 g/cm³
Colors: Orange Brownish-orange
Streak: Yellowish
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Bladed Crystals, Radial Sprays
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Phosphate-rich Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find gatehouseite

Classic worldwide localities

Big Chief mine, South Dakota, USA
Tip Top mine, South Dakota, USA

Field-hunting tip

Look in phosphate-rich pegmatites country — that is the host setting where gatehouseite typically forms. If you start seeing triphylite, hureaulite, rockbridgeite in float, you are in the right ground. Field specimens usually show a bladed crystals, radial sprays habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gatehouseite?+

Mohs hardness is 3-4. It typically shows a vitreous luster. The streak is yellowish. Common colors include orange, brownish-orange.

Where is gatehouseite found?+

Notable localities include Big Chief mine, South Dakota, USA; Tip Top mine, South Dakota, USA.

How much is gatehouseite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like gatehouseite?+

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

What minerals are found with gatehouseite?+

Gatehouseite commonly co-occurs with Triphylite, Hureaulite, Rockbridgeite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gatehouseite form in?+

Gatehouseite typically forms in phosphate-rich pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gatehouseite used for?+

Gatehouseite is used in collector.

Find gatehouseite on the map

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