Sylvanite is a rare gold-silver telluride characterized by its unique graphic, bladed crystal habit that resembles ancient cuneiform or scribbling. It is almost exclusively found in low-temperature hydrothermal gold-telluride deposits and is considered a significant but uncommon ore of gold.
Is this sylvanite?
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 sylvanite with a known reference. Sylvanite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: steel-gray to silver-white.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, brilliant.
- 4Match the color rangeCompare against the expected color range: yellowish silver white, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy, prismatic, skeletal.
Often confused with
Sylvanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Sylvanite leaves steel-gray to silver-white, Calaverite leaves greenish to yellowish gray.
How to tell apart: Streak differs, so Sylvanite leaves steel-gray to silver-white, Krennerite leaves greenish gray; luster reads metallic, brilliant on Sylvanite and very high metallic on Krennerite.
How to tell apart: Streak differs, so Sylvanite leaves steel-gray to silver-white, Petzite leaves grayish black.
Often found alongside sylvanite
Minerals reported to co-occur with sylvanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Au,Ag)₂Te₄
- Mohs hardness
- 1.5-2
- Density
- 8.16 g/cm³
- Colors
- Yellowish silver whiteWhite
- Streak
- Steel-gray to silver-white
- Luster
- Metallic, brilliant
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Platy, prismatic, skeletal
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector, Ore of gold
- Host rock
- Most commonly in low-temperature hydrothermal veins; also in medium- and high-temperature deposits, typically among the last minerals formed
Where rockhounds find sylvanite
3 mapped spotsClassic worldwide localities
- Melones and Stanislaus mines, Carson Hill district, Calaveras Co., California, USA
- Abundance at Cripple Creek, Teller Co., and Magnolia, Gold Hill, and Sunshine districts, Boulder Co., Colorado, USA
- Cornucopia district, Baker Co., Oregon, USA
- Mayflower mine, Tobacco Root Mountains, Madison Co., and the at Gies mine, Judith Mountains, Fergus Co., Montana, USA
- Baia-de-Arieş (Offenbánya) (type locality), Săcărı̂mb (Nagyág) (type locality), and Facebánya, Romania
- Glava, Värmland, Sweden
Field-hunting tip
Where it forms: Most commonly in low-temperature hydrothermal veins; also in medium- and high-temperature deposits, typically among the last minerals formed. If you start seeing gold, calaverite, krennerite in float, you are in the right ground. Typical habit: platy, prismatic, skeletal. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find sylvanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
