Tassieite is a very rare hydrated calcium iron phosphate mineral typically found as small, thin platy crystals or crusts. It is most famous for its occurrence in the tin-bearing deposits of Tasmania, often associated with vivianite in weathered zones.
Is this tassieite?
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 tassieite with a known reference. Tassieite 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. Tassieite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Tassieite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, crusts.
Often confused with
Tassieite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Tassieite leaves light green, Vivianite leaves white to light blue.
How to tell apart: Gorceixite is the harder of the two (Mohs 4.5-5.5 vs. 2); streak differs, so Tassieite leaves light green, Gorceixite leaves white.
Often found alongside tassieite
Minerals reported to co-occur with tassieite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Fe₃(PO₄)₂(OH)₃·15H₂O
- Mohs hardness
- 2
- Density
- 3.45 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Crusts
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Sedimentary Environments
Where rockhounds find tassieite
Classic worldwide localities
- Johnston Fjord, Larsemann Hills, Prydz Bay, East Antarctica
Field-hunting tip
Look in phosphate-rich sedimentary environments country, the host setting where tassieite typically forms. If you start seeing vivianite, siderite, quartz in float, you are in the right ground. Field specimens usually show a platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tassieite?+
Where is tassieite found?+
What rocks look like tassieite?+
What minerals are found with tassieite?+
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Find tassieite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
