Gordonite is a rare hydrated phosphate mineral often found as delicate, colorless to white tabular crystals or radiating sprays. It is most famous among collectors for specimens from the variscite deposits of Fairfield, Utah, where it occurs within phosphate nodules.

Hardness

3.5

Mohs

Luster

Vitreous, pearly on {010}

Streak

White

Transparency

Transparent

mineralrare

Gordonite

Hardness: 3.5
Luster: Vitreous, pearly on {010}
Streak: White
Transparency: Transparent

Is this gordonite?

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 gordonite with a known reference. Gordonite sits at Mohs 3.5, 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: vitreous, pearly on {010}.
4
Match the color range
Compare against the expected color range: colorless, gray white, white, light green, light pink.
5
Look at form & habit
Crystal system: triclinic. Typical habit: encrustations.

Often confused with

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

Often found alongside gordonite

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

All properties

Chemical formula: MgAl₂(PO₄)₂(OH)₂·8H₂O
Mohs hardness: 3.5
Density: 2.23 g/cm³
Colors: Colorless Gray white White Light green Light pink
Streak: White
Luster: Vitreous, pearly on {010}
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Encrustations
Cleavage: {010}, perfect; {100}, fair; {001}, poor
Rarity: Rare
Uses: Collector
Host rock: Rare in variscite-rich phosphate nodules in limestones ([Little Green Monster mine, near] Fairfield, Utah, USA); a late-stage hydrothermal mineral in a complex granite pegmatite (Tip Top mine, South Dakota, USA)

Where rockhounds find gordonite

Classic worldwide localities

Little Green Monster mine, Clay Canyon, about nine km west of Fairfield, Utah Co., Utah, and at the Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
Rapid Creek, Yukon Territory, Canada
Sapucaia pegmatite mine, about 50 km east-southeast of Governador Valadares, Minas Gerais, Brazil
Mt. Vasin-Myl’k, Voron’i massif, Kola Peninsula, Russia

Field-hunting tip

Where it forms: Rare in variscite-rich phosphate nodules in limestones ([Little Green Monster mine, near] Fairfield, Utah, USA); a late-stage hydrothermal mineral in a complex granite pegmatite (Tip Top mine, South Dakota, USA). If you start seeing variscite, crandallite, wardite in float, you are in the right ground. Typical habit: encrustations. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gordonite?+

Mohs hardness is 3.5. Luster: vitreous, pearly on {010}. The streak is white. Common colors include colorless, gray white, white, light green.

Where is gordonite found?+

Notable localities include Little Green Monster mine, Clay Canyon, about nine km west of Fairfield, Utah Co., Utah, and at the Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA; Rapid Creek, Yukon Territory, Canada; Sapucaia pegmatite mine, about 50 km east-southeast of Governador Valadares, Minas Gerais, Brazil; Mt. Vasin-Myl’k, Voron’i massif, Kola Peninsula, Russia.

What rocks look like gordonite?+

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

What minerals are found with gordonite?+

Gordonite commonly co-occurs with Variscite, Crandallite, Wardite, Robertsite, Collinsite, Montgomeryite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gordonite form in?+

Where it forms: Rare in variscite-rich phosphate nodules in limestones ([Little Green Monster mine, near] Fairfield, Utah, USA); a late-stage hydrothermal mineral in a complex granite pegmatite (Tip Top mine, South Dakota, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is gordonite used for?+

Gordonite is used in collector.

Find gordonite on the map

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