Siwaqaite is a rare member of the ettringite group typically found as delicate, needle-like acicular crystals. It is primarily known from the Siwaqa area of Jordan, where it forms in highly specific geological settings involving thermal metamorphism. Collectors should handle specimens with care due to their fragility and susceptibility to dehydration.
Is this siwaqaite?
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 siwaqaite with a known reference. Siwaqaite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellowish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: canary-yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: acicular crystals.
Often confused with
Siwaqaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Siwaqaite leaves yellowish gray, Ettringite leaves white.
How to tell apart: Thaumasite is the harder of the two (Mohs 3.5 vs. ~2); streak differs, so Siwaqaite leaves yellowish gray, Thaumasite leaves white.
Often found alongside siwaqaite
Minerals reported to co-occur with siwaqaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₆Al₂(CrO₄)₃(OH)₁₂·26H₂O
- Mohs hardness
- ~2
- Density
- 1.819 g/cm³
- Colors
- Streak
- Yellowish gray
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Acicular crystals
- Cleavage
- Perfect on {101̄0}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In thin veins and small cavities in spurrite marble of a high-temperature low-pressure pyrometamorphic sequence of rocks
Where rockhounds find siwaqaite
Classic worldwide localities
- North Siwaqa complex, Lisdan-Siwaqa Fault, Hashem region, 60 km south of Amman, Jordan
Field-hunting tip
Where it forms: In thin veins and small cavities in spurrite marble of a high-temperature low-pressure pyrometamorphic sequence of rocks. If you start seeing calcite, fluorapatite, brownmillerite in float, you are in the right ground. Typical habit: acicular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find siwaqaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
