Koechlinite is a rare secondary bismuth molybdate mineral that typically forms as small, thin, platy crystals or earthy, micaceous coatings. It is most commonly found in the oxidation zones of bismuth-molybdenum hydrothermal deposits, often appearing as distinct yellowish scales associated with other secondary bismuth minerals.
Is this koechlinite?
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 koechlinite with a known reference. Koechlinite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale greenish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: yellow, greenish yellow, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, micaceous masses.
Often confused with
Koechlinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Koechlinite leaves pale greenish yellow, Bismutite leaves gray; luster reads silky on Koechlinite and vitreous, waxy, may be dull to earthy on Bismutite.
How to tell apart: Koechlinite is noticeably harder (Mohs 3 vs. 1-2); luster reads silky on Koechlinite and adamantine to silky, earthy on Ferrimolybdite.
Often found alongside koechlinite
Minerals reported to co-occur with koechlinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂MoO₆
- Mohs hardness
- 3
- Density
- 8.26 g/cm³
- Streak
- Pale greenish yellow
- Luster
- Silky
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy crystals, micaceous masses
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As a rare alteration product in the oxidation zone of Bi–Mo deposits
Where rockhounds find koechlinite
Classic worldwide localities
- Outlaw mine, Mariposa Canyon, Round Mountain district, Nye Co., Nevada, and from the Climax mine, Lake Co., Colorado, USA
- Daniel mine, Schneeberg, Saxony, and the Clara mine, near Oberwolfach, Black Forest, Germany
- Cínovec (Zinnwald), Czech Republic
- Sa Duchessa mine, Oridda district, Sardinia, Italy
- Kerrouchene tungsten mine, Middle Atlas Mountains, Morocco
- Torgovsk Bi–Mo–W mine, Polar Ural Mountains, Russia
Field-hunting tip
Where it forms: As a rare alteration product in the oxidation zone of Bi–Mo deposits. If you start seeing bismuth, skutterudite, quartz in float, you are in the right ground. Typical habit: platy crystals, micaceous masses. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify koechlinite?+
Where is koechlinite found?+
Is koechlinite safe to handle?+
What rocks look like koechlinite?+
What minerals are found with koechlinite?+
What kind of rock does koechlinite form in?+
What is koechlinite used for?+
Find koechlinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
