Lumsdenite is a rare sodium calcium magnesium oxide, typically dark green-blue. It is a post-mining secondary crust on asphaltum in montroseite- and corvusite-bearing sandstone. Associated minerals include gypsum, huemulite and rosslerite. It was first described from Packrat mine, Lumsden Canyon, near Gateway, Mesa Co., Colorado, USA.
Is this lumsdenite?
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 lumsdenite with a known reference. Lumsdenite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lumsdenite leaves a green-blue streak.
- 3Read the lusterHold the specimen under a strong light. Lumsdenite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green-blue.
- 5Look at form & habitCrystal system: triclinic. Typical habit: massive, granular.
Often confused with
Lumsdenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Lumsdenite leaves green-blue, Stannite leaves blackish; luster reads vitreous on Lumsdenite and metallic on Stannite.
How to tell apart: Streak differs, so Lumsdenite leaves green-blue, Tetrahedrite leaves black; luster reads vitreous on Lumsdenite and metallic on Tetrahedrite.
Often found alongside lumsdenite
Minerals reported to co-occur with lumsdenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₃Mg₂(H₂O)₃₁(As³⁺V⁴⁺₂V⁵⁺₁₀As⁵⁺₆O₅₁)·14H₂O
- Mohs hardness
- 3.5
- Density
- 2.35 g/cm³
- Colors
- Streak
- Green-blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
Where rockhounds find lumsdenite
Classic worldwide localities
- Lumsden Mine, Canada
- various epithermal vein deposits
Field-hunting tip
Look in hydrothermal veins country, the host setting where lumsdenite typically forms. If you start seeing quartz, pyrite, chalcopyrite in float, you are in the right ground. Field specimens usually show a massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify lumsdenite?+
Where is lumsdenite found?+
Is lumsdenite safe to handle?+
What rocks look like lumsdenite?+
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Find lumsdenite on the map
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