Rudenkoite is a rare strontium aluminum hydroxide, typically white. Associated minerals include prehnite, calcite and spinel. It was first described from Emelʼdzhaksky phlogopite deposit, Aldan province, Aldan Shield, southern Yakutsk, Russia.
Is this rudenkoite?
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 rudenkoite with a known reference. Rudenkoite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rudenkoite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rudenkoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, thin plates, coatings.
Often confused with
Rudenkoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Laurionite is the harder of the two (Mohs 3-3.5 vs. 1.5); luster reads vitreous on Rudenkoite and adamantine on Laurionite.
How to tell apart: Penfieldite is the harder of the two (Mohs 2.5 vs. 1.5); luster reads vitreous on Rudenkoite and adamantine on Penfieldite.
How to tell apart: Paralaurionite is the harder of the two (Mohs 2.5 vs. 1.5); luster reads vitreous on Rudenkoite and subadamantine on Paralaurionite.
Often found alongside rudenkoite
Minerals reported to co-occur with rudenkoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sr₃Al₃.₅Si₃.₅O₁₀(OH,O)₈Cl₂·H₂O
- Mohs hardness
- 1.5
- Density
- 3.17 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Thin Plates, Coatings
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Lead-zinc Deposits
Where rockhounds find rudenkoite
Classic worldwide localities
- Kadyrelskoye Pb-Zn deposit, Tuva, Russia
Field-hunting tip
Look in oxidized lead-zinc deposits country, the host setting where rudenkoite typically forms. If you start seeing galena, cerussite, anglesite in float, you are in the right ground. Field specimens usually show a tabular crystals, thin plates, coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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