Romarchite is a rare tin oxide mineral typically found in the oxidation zones of tin deposits. It is often identified by its distinct black to dark-brown platy crystals and high density resulting from its tin content. Collectors primarily seek it as an uncommon mineral species associated with historical mining artifacts or oxidized hydrothermal veins.
Is this romarchite?
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 romarchite with a known reference. Romarchite sits at Mohs 2-2.5, 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: submetallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: acicular, encrustations, microscopic crystals.
Often confused with
Romarchite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Cassiterite is the harder of the two (Mohs 6-7 vs. 2-2.5); streak differs, so Romarchite leaves black, Cassiterite leaves white, pale brown, pale gray; luster reads submetallic on Romarchite and adamantine to adamantine metallic, splendent; may be greasy on fractures on Cassiterite.
How to tell apart: Streak differs, so Romarchite leaves black, Hydroromarchite leaves white; luster reads submetallic on Romarchite and adamantine on Hydroromarchite.
Often found alongside romarchite
Minerals reported to co-occur with romarchite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SnO
- Mohs hardness
- 2-2.5
- Density
- 6.40 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Semitransparent
- Crystal system
- Tetragonal
- Crystal habit
- Acicular, encrustations, microscopic crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector, Scientific
- Host rock
- As an alteration product on tin pannikins immersed in a river (Boundary Falls, Canada); replacing herzenbergite replacing cassiterite (Maria-Teresa mine, Bolivia)
Where rockhounds find romarchite
Classic worldwide localities
- Boundary Falls, Winnipeg River, Ontario, Canada, where tin pannikins had been dropped by a voyageur between 1801 and 1821
- Maria-Teresa mine, near Huari, between Oruro and Uyuni, Bolivia
- A cove of the Red Sea known as Sharm Abhur, about 30 km north of Jiddah, Saudi Arabia
Field-hunting tip
Where it forms: As an alteration product on tin pannikins immersed in a river (Boundary Falls, Canada); replacing herzenbergite replacing cassiterite (Maria-Teresa mine, Bolivia). If you start seeing hydroromarchite, abhurite, kutnohorite in float, you are in the right ground. Typical habit: acicular, encrustations, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find romarchite on the map
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