Sterlinghillite is an extremely rare manganese arsenate mineral known primarily from the famous Sterling Hill Mine. It usually occurs as microscopic, white to colorless platy crystals or crusts that are best identified by their characteristic bright white fluorescence under short-wave UV light.

Hardness

Mohs

Luster

Dull to silky

Streak

White

Transparency

Semitransparent

mineralrare

Sterlinghillite

Hardness: 3
Luster: Dull to silky
Streak: White
Transparency: Semitransparent

Is this sterlinghillite?

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 sterlinghillite with a known reference. Sterlinghillite sits at Mohs 3, 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: dull to silky.
4
Match the color range
Compare against the expected color range: white, light pink.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: spherical, tabular.

Often confused with

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

mineral

Austinite

Mohs 4-4.5

How to tell apart: Austinite is the harder of the two (Mohs 4-4.5 vs. 3); luster reads dull to silky on Sterlinghillite and subadamantine to silky in aggregates on Austinite.

Compare →

Often found alongside sterlinghillite

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

All properties

Chemical formula: Mn₃(AsO₄)₂·3H₂O
Mohs hardness: 3
Density: 2.95 g/cm³
Colors: White Light pink
Streak: White
Luster: Dull to silky
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Spherical, tabular
Cleavage: One, perfect, parallel to elongation
Fluorescence: Bright white under SW UV
Rarity: Rare
Uses: Collector
Host rock: A very rare mineral in seams in franklinite ore from a metamorphosed stratiform zinc orebody

Where rockhounds find sterlinghillite

Classic worldwide localities

Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA

Field-hunting tip

Where it forms: A very rare mineral in seams in franklinite ore from a metamorphosed stratiform zinc orebody. If you start seeing franklinite, sphalerite, löllingite in float, you are in the right ground. Typical habit: spherical, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sterlinghillite?+

Mohs hardness is 3. Luster: dull to silky. The streak is white. Common colors include white, light pink.

Where is sterlinghillite found?+

Notable localities include Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA.

Is sterlinghillite safe to handle?+

Sterlinghillite contains arsenic and calls for real care. Contains arsenic, a toxic element. Handle with care, avoid creating dust, and wash hands thoroughly after handling.

What rocks look like sterlinghillite?+

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

What minerals are found with sterlinghillite?+

Sterlinghillite commonly co-occurs with Franklinite, Sphalerite, Löllingite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sterlinghillite form in?+

Where it forms: A very rare mineral in seams in franklinite ore from a metamorphosed stratiform zinc orebody. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sterlinghillite used for?+

Sterlinghillite is used in collector.

Find sterlinghillite on the map

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