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. Streak: green-blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 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 to brown; luster reads vitreous on Lumsdenite and metallic, commonly splendent 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
- Dark green-blue
- 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
Where it forms: hydrothermal veins. If you start seeing quartz, pyrite, chalcopyrite in float, you are in the right ground. Typical habit: massive, granular. 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?+
What minerals are found with lumsdenite?+
What kind of rock does lumsdenite form in?+
What is lumsdenite used for?+
Find lumsdenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
