Gratonite is a rare lead arsenic sulfide mineral typically found as small, lead-gray prismatic crystals. It is almost exclusively associated with the lead-zinc deposits of the Cerro de Pasco district in Peru. Due to its high lead and arsenic content, collectors should exercise caution and handle specimens with care.

Hardness

2.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Gratonite

Hardness: 2.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this gratonite?

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 gratonite with a known reference. Gratonite 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. Gratonite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Gratonite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: lead-gray, dark gray.
5
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals, acicular, granular.

Often confused with

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

mineral

Galena

Mohs 2.5

How to tell apart: Streak differs, so Gratonite leaves black, Galena leaves lead-gray.

How to tell apart: Streak differs, so Gratonite leaves black, Boulangerite leaves brownish-gray.

How to tell apart: Streak differs, so Gratonite leaves black, Jamesonite leaves gray-black.

Compare →

Often found alongside gratonite

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

All properties

Chemical formula: Pb₉As₄S₁₅
Mohs hardness: 2.5
Density: 6.25 g/cm³
Colors: Lead-gray Dark Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Prismatic Crystals, Acicular, Granular
Cleavage: Poor
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Sulfide Veins
Typical price: $50-300 per thumbnail or small specimen

Where rockhounds find gratonite

Classic worldwide localities

Excelsior Mine, Cerro de Pasco, Peru

Field-hunting tip

Look in hydrothermal sulfide veins country, the host setting where gratonite typically forms. If you start seeing galena, pyrite, sphalerite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gratonite?+

Mohs hardness is 2.5. It typically shows a metallic luster. The streak is black. Common colors include lead-gray, dark gray.

Where is gratonite found?+

Notable localities include Excelsior Mine, Cerro de Pasco, Peru.

How much is gratonite worth?+

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

Is gratonite safe to handle?+

It contains toxic constituents. Contains lead and arsenic; avoid inhalation of dust, wash hands thoroughly after handling, and store in a sealed container. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like gratonite?+

Gratonite is most often confused with Galena, Boulangerite, Jamesonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with gratonite?+

Gratonite commonly co-occurs with Galena, Pyrite, Sphalerite, Arsenopyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gratonite form in?+

Gratonite typically forms in hydrothermal sulfide veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gratonite used for?+

Gratonite is used in collector.

Find gratonite on the map

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