Ferrobustamite is a member of the wollastonite group characterized by its iron-rich composition. It typically occurs in skarn deposits formed through the contact metamorphism of impure limestones, often appearing as fibrous or granular masses that can be difficult to distinguish from common wollastonite without chemical testing.
Is this ferrobustamite?
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 ferrobustamite with a known reference. Ferrobustamite sits at Mohs 6, 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: green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: massive.
Often confused with
Ferrobustamite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Ferrobustamite is noticeably harder (Mohs 6 vs. 4.5-5).
How to tell apart: Ferrobustamite is noticeably harder (Mohs 6 vs. 4.5-5); luster reads vitreous on Ferrobustamite and silky, subvitreous on Pectolite.
Often found alongside ferrobustamite
Minerals reported to co-occur with ferrobustamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaFeSi₂O₆
- Mohs hardness
- 6
- Density
- 3.09 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Massive
- Cleavage
- {100}, perfect; {110}, {110}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Surrounding chert nodules in a skarn in dolostone (Isle of Skye, Scotland)
Where rockhounds find ferrobustamite
Classic worldwide localities
- Camas Malag, Isle of Skye, Scotland
- Scawt Hill, near Larne, Co. Antrim, Ireland
- Kagata, Ofuku, and Ohta mines, Yamaguchi Prefecture, Japan
- Kasugayama and Tsuchiarashi deposits, near Iida, Nagano Prefecture, Japan
- Kurodaké Peak, near Toyama, Yoyama Prefecture, Japan
- Tsumo mine, Shimane Prefecture, Japan
Field-hunting tip
Where it forms: Surrounding chert nodules in a skarn in dolostone (Isle of Skye, Scotland). If you start seeing hedenbergite, grossular-andradite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrobustamite?+
Where is ferrobustamite found?+
What rocks look like ferrobustamite?+
What minerals are found with ferrobustamite?+
What kind of rock does ferrobustamite form in?+
What is ferrobustamite used for?+
Find ferrobustamite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
