Gillespite is a rare barium iron silicate known for its distinct, vibrant red color and tabular, micaceous crystal habit. It is primarily sought after by advanced collectors for its striking appearance and rarity, typically occurring in association with sanbornite in metamorphic complexes.
Is this gillespite?
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 gillespite with a known reference. Gillespite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pink.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: red.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: aggregates.
Often confused with
Gillespite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Gillespite leaves pink, Witherite leaves white.
How to tell apart: Sanbornite is the harder of the two (Mohs 5 vs. 3-4); streak differs, so Gillespite leaves pink, Sanbornite leaves white; luster reads vitreous on Gillespite and pearly on Sanbornite.
Often found alongside gillespite
Minerals reported to co-occur with gillespite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaFeSi₄O₁₀
- Mohs hardness
- 3-4
- Density
- 3.390-3.402 g/cm³
- Colors
- Streak
- Pink
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Aggregates
- Cleavage
- Very good on {001}, poor on {100}; very poor on {110}
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- In a glacial moraine (Dry Delta, Alaska, USA); probably from a contact metamorphic zone (Trumbull Peak, California, USA)
Where rockhounds find gillespite
Classic worldwide localities
- Head of Dry Delta, Alaska Range, USA
- Trumbull Peak, near Incline, Mariposa Co., and on the Esquire No. 7 claim, Big Creek, Fresno Co., California, USA
- Gunn claim, in the Itsy Mountains, near Macmillan Pass, Yukon Territory, Canada
- La Madrelena mine, Tres Pozos, Baja California, Mexico
Field-hunting tip
Where it forms: In a glacial moraine (Dry Delta, Alaska, USA); probably from a contact metamorphic zone (Trumbull Peak, California, USA). If you start seeing celsian, hedenbergite, quartz in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find gillespite on the map
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