Stewartite is a rare phosphate mineral often found as an alteration product of triphylite in phosphate-rich pegmatites. It typically appears as orange, fibrous, or bladed crystal aggregates and is highly sought after by systematic mineral collectors.
Is this stewartite?
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 stewartite with a known reference. Stewartite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Stewartite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Stewartite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: orange, reddish-orange, brownish-orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: bladed, fibrous aggregates, crusts.
Often confused with
Stewartite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside stewartite
Minerals reported to co-occur with stewartite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺Fe³⁺₂(PO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 1.5-2
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Bladed, Fibrous Aggregates, Crusts
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 for micro-mounts or small specimens
Where rockhounds find stewartite
Classic worldwide localities
- Stewart Mine, Pala, California, USA
- Hagendorf-Pleystein, Bavaria, Germany
- Mangualde, Viseu, Portugal
- Sapucaia Mine, Minas Gerais, Brazil
Field-hunting tip
Look in granite pegmatites country — that is the host setting where stewartite typically forms. If you start seeing sicklerite, triphylite, hureaulite in float, you are in the right ground. Field specimens usually show a bladed, fibrous aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify stewartite?+
Where is stewartite found?+
How much is stewartite worth?+
What rocks look like stewartite?+
What minerals are found with stewartite?+
What kind of rock does stewartite form in?+
What is stewartite used for?+
Find stewartite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
