Maxwellite is an extremely rare arsenic-bearing mineral found primarily in the Thomas Range of Utah. It typically occurs as small, bladed crystals within gas cavities of rhyolite flows, frequently associated with other rare topaz-related minerals.
Is this maxwellite?
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 maxwellite with a known reference. Maxwellite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: medium to pale red-orange.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, prismatic.
Often confused with
Maxwellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Maxwellite leaves medium to pale red-orange, Tilasite leaves white; luster reads vitreous on Maxwellite and resinous, vitreous on cleavages on Tilasite.
How to tell apart: Streak differs, so Maxwellite leaves medium to pale red-orange, Durangite leaves cream-yellow to pale yellow.
Often found alongside maxwellite
Minerals reported to co-occur with maxwellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaFeAsO₄F
- Mohs hardness
- 5-5.5
- Density
- 3.90 g/cm³
- Colors
- Streak
- Medium to pale red-orange
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, prismatic
- Cleavage
- Good on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Rarely formed in miarolitic cavities in rhyolite adjacent to high-temperature veins in hydrothermal tin deposits
Where rockhounds find maxwellite
Classic worldwide localities
- Squaw Creek tin prospect, Catron Co., and in Willow Spring Draw, Sierra Co., Taylor Creek district, New Mexico, USA
Field-hunting tip
Where it forms: Rarely formed in miarolitic cavities in rhyolite adjacent to high-temperature veins in hydrothermal tin deposits. If you start seeing squawcreekite, cassiterite, hematite in float, you are in the right ground. Typical habit: aggregates, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify maxwellite?+
Where is maxwellite found?+
Is maxwellite safe to handle?+
What rocks look like maxwellite?+
What minerals are found with maxwellite?+
What kind of rock does maxwellite form in?+
What is maxwellite used for?+
Find maxwellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
