Ferdowsiite is an extremely rare silver-antimony-telluride sulfide mineral first discovered in the Kuh-e-Shah region of Iran. It typically occurs as microscopic anhedral grains associated with other sulfide minerals in epithermal vein deposits. Due to its extreme rarity, it is primarily of interest to advanced professional mineralogists and specialized systematic collectors.
Is this ferdowsiite?
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 ferdowsiite with a known reference. Ferdowsiite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: grayish black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains.
Often confused with
Ferdowsiite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferdowsiite leaves dark gray, Tetrahedrite leaves black to brown.
How to tell apart: Streak differs, so Ferdowsiite leaves dark gray, Stibnite leaves lead-gray.
How to tell apart: Streak differs, so Ferdowsiite leaves dark gray, Acanthite leaves black.
Often found alongside ferdowsiite
Minerals reported to co-occur with ferdowsiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₈(Sb₅As₃)S₁₆
- Mohs hardness
- 2.5-3
- Density
- 5.3 g/cm³
- Colors
- Streak
- Dark gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In barite-quartz lenses in a metamorphosed strataform volcanogenic massive sulfide deposit
Where rockhounds find ferdowsiite
Classic worldwide localities
- Barika gold deposit, 17 km East of Sardasht, West Azerbaijan province, NW Iran
Field-hunting tip
Where it forms: In barite-quartz lenses in a metamorphosed strataform volcanogenic massive sulfide deposit. If you start seeing barite, ferroan tetrahedrite-tennantite, smithite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferdowsiite?+
Where is ferdowsiite found?+
Is ferdowsiite safe to handle?+
What rocks look like ferdowsiite?+
What minerals are found with ferdowsiite?+
What kind of rock does ferdowsiite form in?+
What is ferdowsiite used for?+
Find ferdowsiite on the map
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