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.
Is this gratonite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch gratonite with a known reference. Gratonite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: lead gray, dark lead gray.
- 5Look at form & habitCrystal 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.
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.
How to tell apart: Streak differs, so Gratonite leaves black, Jamesonite leaves black. grayish.
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
- 6.22 g/cm³
- Colors
- Lead grayDark lead gray
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Prismatic crystals, acicular, granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In vugs in hydrothermal copper ores
Where rockhounds find gratonite
Classic worldwide localities
- Excelsior mine, Cerro de Pasco, Peru (type locality)
- Santa Lucia deposit, Cuba
- Blei-Scharley mine, Upper Silesia, Poland
- Zvezdel, Bulgaria
- Wiesloch, near Heidelberg, Black Forest, Germany
- Lengenbach quarry, Binntal, Valais, Switzerland
Field-hunting tip
Where it forms: In vugs in hydrothermal copper ores. If you start seeing realgar, pyrite, sphalerite in float, you are in the right ground. Typical habit: prismatic crystals, acicular, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gratonite?+
Where is gratonite found?+
Is gratonite safe to handle?+
What rocks look like gratonite?+
What minerals are found with gratonite?+
What kind of rock does gratonite form in?+
What is gratonite used for?+
Find gratonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
