Ruifrancoite is a rare phosphate mineral primarily found in granitic pegmatites. It typically occurs as small tabular crystals associated with other phosphate minerals, often requiring microscopic examination for positive identification due to its similarity to other members of the fillowite group.
Is this ruifrancoite?
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 ruifrancoite with a known reference. Ruifrancoite 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: orange-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, botryoidal, lath.
Often confused with
Ruifrancoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ruifrancoite leaves orange-brown, Fillowite leaves white; luster reads vitreous on Ruifrancoite and subresinous to greasy on Fillowite.
How to tell apart: Streak differs, so Ruifrancoite leaves orange-brown, Johnsomervilleite leaves pale brown; gray-brown with an olive tint.
Often found alongside ruifrancoite
Minerals reported to co-occur with ruifrancoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂(☐,Mn)₂(Fe³⁺,Mn,Mg)₄Be₄(PO₄)₆(OH)₆·4H₂O
- Mohs hardness
- ~4.5
- Density
- 2.88 g/cm³
- Colors
- Streak
- Orange-brown
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, botryoidal, lath
- Cleavage
- Perfect on {100}, good on {010} (by analogy to other roscherite-group minerals)
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late, vug-filling phase in a zoned LCT-type granitic pegmatite
Where rockhounds find ruifrancoite
Classic worldwide localities
- Sapucaia mine, Minas Gerais, Brazil (type locality)
Field-hunting tip
Where it forms: A late, vug-filling phase in a zoned LCT-type granitic pegmatite. If you start seeing albite, muscovite, cyrilovite in float, you are in the right ground. Typical habit: acicular, botryoidal, lath. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ruifrancoite?+
Where is ruifrancoite found?+
Is ruifrancoite safe to handle?+
What rocks look like ruifrancoite?+
What minerals are found with ruifrancoite?+
What kind of rock does ruifrancoite form in?+
What is ruifrancoite used for?+
Find ruifrancoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
