Fresnoite is a rare barium titanium silicate mineral most famously found in the Sanbornite-bearing metamorphic rocks of California. It typically appears as small, lustrous yellow-orange crystals that exhibit a diagnostic bright yellow-green fluorescence under short-wave ultraviolet light.
Is this fresnoite?
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 fresnoite with a known reference. Fresnoite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: greenish yellow, lemon.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic, tabular, or granular.
Often confused with
Fresnoite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside fresnoite
Minerals reported to co-occur with fresnoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ba₂TiSi₂O₈
- Mohs hardness
- 3-4
- Density
- 4.43 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic, tabular, or granular
- Cleavage
- Fair on {001}
- Fluorescence
- Yellow under SW UV
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Disseminated in gneissic metamorphic rocks composed mainly of sanbornite and quartz (Rush Creek, California, USA)
Where rockhounds find fresnoite
Classic worldwide localities
- Rush Creek area and at the Esquire No. 1 mine, Big Creek, Fresno Co., California, USA
- Gem mine, and in the Clear Creek district, at the Victor mine, and Junilla mine, San Benito Co., California, USA
- Trumbull Peak, near Incline, Mariposa Co., California, USA
- Gunn claim, Itsy Mountains, near Macmillan Pass, Yukon Territory, Canada
- Graulai and Üdersdorf, Eifel district, Germany
Field-hunting tip
Where it forms: Disseminated in gneissic metamorphic rocks composed mainly of sanbornite and quartz (Rush Creek, California, USA). If you start seeing quartz, sanbornite, celsian in float, you are in the right ground. Typical habit: prismatic, tabular, or granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fresnoite?+
Where is fresnoite found?+
What rocks look like fresnoite?+
What minerals are found with fresnoite?+
What kind of rock does fresnoite form in?+
What is fresnoite used for?+
Find fresnoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
