Koktaite is a rare sulfate mineral that typically forms as white to colorless efflorescences or small, thin tabular crystals in self-burning coal mine waste heaps. It is chemically related to syngenite but contains ammonium as a major cation, making it a distinct phase often found in ephemeral environments. Due to its solubility, it is best kept in a dry environment and protected from high humidity.
Is this koktaite?
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 koktaite with a known reference. Koktaite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, fibrous, water soluble.
Often confused with
Koktaite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside koktaite
Minerals reported to co-occur with koktaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Ca(SO₄)₂·H₂O
- Mohs hardness
- 2
- Density
- 2.09 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, fibrous, water soluble
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- On waste piles of a lignite mine
Where rockhounds find koktaite
Classic worldwide localities
- Žeravice, near Kyjov, Czech Republic
Field-hunting tip
Where it forms: On waste piles of a lignite mine. If you start seeing gypsum, mascagnite, tschermigite in float, you are in the right ground. Typical habit: acicular, fibrous, water soluble. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify koktaite?+
Where is koktaite found?+
What rocks look like koktaite?+
What minerals are found with koktaite?+
What kind of rock does koktaite form in?+
What is koktaite used for?+
Find koktaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
