Allargentum is a rare silver-antimony intermetallic mineral often found as intimate intergrowths with dyscrasite and native silver. Collectors should look for its distinctive bright silver-white metallic luster in hydrothermal vein deposits. It is best identified through micro-analysis as it is visually indistinguishable from other silver-antimony minerals without specialized testing.
Is this allargentum?
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 allargentum with a known reference. Allargentum sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: silver-white.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: silver gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: massive, anhedral grains, blebs.
Often confused with
Allargentum vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside allargentum
Minerals reported to co-occur with allargentum. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₁-ₓSbₓ
- Mohs hardness
- 4
- Density
- 10.0 g/cm³
- Colors
- Streak
- Silver-white
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Massive, anhedral grains, blebs
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In high-grade Ag–Sb ores
Where rockhounds find allargentum
Classic worldwide localities
- Calliope mine, Ouray district, Ouray Co., Colorado, USA
- Hi-Ho mine, Cobalt (type locality), and many mines of the Cobalt district, Ontario, Canada
- Red Lake area, Ontario, Canada
- Consols and Junction mines, Broken Hill, New South Wales, and North Arm, Queensland, Australia
- Wasserfall, about 20 km northwest of Belfort, Haute-Saône, France
- Rejská, near Kutná Hora, and at Příbram, Czech Republic
Field-hunting tip
Where it forms: In high-grade Ag–Sb ores. If you start seeing dyscrasite, breithauptite, domeykite in float, you are in the right ground. Typical habit: massive, anhedral grains, blebs. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify allargentum?+
Where is allargentum found?+
Is allargentum safe to handle?+
What rocks look like allargentum?+
What minerals are found with allargentum?+
What kind of rock does allargentum form in?+
What is allargentum used for?+
Find allargentum on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
