Borocookeite is a rare lithium-bearing silicate mineral belonging to the chlorite group, characterized by its inclusion of boron. It typically forms thin, micaceous plates or flaky aggregates within complex granitic pegmatites. Collectors look for it associated with other late-stage pegmatite minerals like tourmaline and albite.
Is this borocookeite?
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 borocookeite with a known reference. Borocookeite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Borocookeite leaves a light pinkish gray streak.
- 3Read the lusterHold the specimen under a strong light. Borocookeite typically shows a greasy luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy or micaceous aggregates.
Often confused with
Borocookeite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Borocookeite leaves light pinkish gray, Cookeite leaves white; luster reads greasy on Borocookeite and pearly on Cookeite.
How to tell apart: Streak differs, so Borocookeite leaves light pinkish gray, Muscovite leaves white; luster reads greasy on Borocookeite and pearly on Muscovite.
How to tell apart: Streak differs, so Borocookeite leaves light pinkish gray, Lepidolite leaves white; luster reads greasy on Borocookeite and pearly on Lepidolite.
Often found alongside borocookeite
Minerals reported to co-occur with borocookeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Li₂Al₄(Si₃B)O₁₀(OH)₈
- Mohs hardness
- 2-2.5
- Density
- 2.7-2.8 g/cm³
- Streak
- Light Pinkish Gray
- Luster
- Greasy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy or Micaceous Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
Where rockhounds find borocookeite
Classic worldwide localities
- San Piero in Campo, Elba, Italy
- Mount Mica, Maine, USA
- Siberia, Russia
Field-hunting tip
Look in granite pegmatites country, the host setting where borocookeite typically forms. If you start seeing tourmaline, quartz, albite in float, you are in the right ground. Field specimens usually show a platy or micaceous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify borocookeite?+
Where is borocookeite found?+
What rocks look like borocookeite?+
What minerals are found with borocookeite?+
What kind of rock does borocookeite form in?+
What is borocookeite used for?+
Find borocookeite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
