Caysichite-(Y) is an exceptionally rare yttrium-bearing silicate-carbonate mineral typically found in complex alkaline pegmatites. Collectors usually search for it as tiny acicular, radiating clusters or crusts coating other pegmatite minerals. It is highly sought after by systematic mineral collectors due to its limited distribution and complex chemical composition.
Is this caysichite-(y)?
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 caysichite-(y) with a known reference. Caysichite-(Y) sits at Mohs 4.5, 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: white, colorless, green, greenish yellow, light yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pulverulent, reniform, stalactitic.
Often confused with
Caysichite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Stillwellite-(Ce) is the harder of the two (Mohs ~6.5 vs. 4.5); luster reads vitreous on Caysichite-(Y) and resinous on Stillwellite-(Ce).
How to tell apart: Allanite is the harder of the two (Mohs 5.5-6 vs. 4.5); streak differs, so Caysichite-(Y) leaves white, Allanite leaves gray; luster reads vitreous on Caysichite-(Y) and submetallic on Allanite.
Often found alongside caysichite-(y)
Minerals reported to co-occur with caysichite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Yb,Er)₄Y₄Si₈O₂₀(CO₃)₆(OH)·7H₂O
- Mohs hardness
- 4.5
- Density
- 3.03 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Pulverulent, reniform, stalactitic
- Cleavage
- {010} (?)
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In perthite surrounding the quartz core of a granite pegmatite, coating fractures and filling cavities in quartz, perthite, or hellandite; apparently of secondary origin
Where rockhounds find caysichite-(y)
Classic worldwide localities
- Evans-Lou quarry, near Wakefield Lake, Quebec, Canada
Field-hunting tip
Where it forms: In perthite surrounding the quartz core of a granite pegmatite, coating fractures and filling cavities in quartz, perthite, or hellandite; apparently of secondary origin. If you start seeing quartz, hellandite, fergusonite in float, you are in the right ground. Typical habit: pulverulent, reniform, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify caysichite-(y)?+
Where is caysichite-(y) found?+
What rocks look like caysichite-(y)?+
What minerals are found with caysichite-(y)?+
What kind of rock does caysichite-(y) form in?+
What is caysichite-(y) used for?+
Find caysichite-(y) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
