Dissakisite-(La) is a rare lanthanum-dominant member of the epidote group, often occurring as small, dark, prismatic crystals in metamorphic environments. It is visually indistinguishable from other allanite-group minerals in the field and typically requires chemical analysis for definitive identification. Collectors often seek it out for its significance as a rare earth element-bearing mineral species.
Is this dissakisite-(la)?
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 dissakisite-(la) with a known reference. Dissakisite-(La) sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray-greenish.
- 3Read the lusterHold the specimen under a strong light. Luster: pitch-like to vitreous.
- 4Match the color rangeCompare against the expected color range: black, very dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, anhedral grains, inclusions.
Often confused with
Dissakisite-(La) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Dissakisite-(La) leaves gray-greenish, Epidote leaves grayish white; luster reads pitch-like to vitreous on Dissakisite-(La) and vitreous, pearly, somewhat resinous on Epidote.
How to tell apart: Streak differs, so Dissakisite-(La) leaves gray-greenish, Allanite-(Ce) leaves gray; luster reads pitch-like to vitreous on Dissakisite-(La) and vitreous, resinous to submetallic on Allanite-(Ce).
How to tell apart: Streak differs, so Dissakisite-(La) leaves gray-greenish, Clinozoisite leaves grayish white; luster reads pitch-like to vitreous on Dissakisite-(La) and vitreous on Clinozoisite.
Often found alongside dissakisite-(la)
Minerals reported to co-occur with dissakisite-(la). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaLaMgAl₂(Si₂O₇)(SiO₄)O(OH)
- Mohs hardness
- 6.5-7
- Density
- 3.79 g/cm³
- Colors
- BlackVery dark brown
- Streak
- Gray-greenish
- Luster
- Pitch-like to vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, anhedral grains, inclusions
- Cleavage
- Imperfect on (001)
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- By hydration and enrichment in LILE and LREE of a garnet-bearing peridotite body, in relation to HP-migmatization of the surrounding gneisses during an orogeny
Where rockhounds find dissakisite-(la)
Classic worldwide localities
- Japan
- Norway
- Italy
- United States
Field-hunting tip
Where it forms: By hydration and enrichment in LILE and LREE of a garnet-bearing peridotite body, in relation to HP-migmatization of the surrounding gneisses during an orogeny. If you start seeing olivine, spinel, amphiboles in float, you are in the right ground. Typical habit: aggregates, anhedral grains, inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify dissakisite-(la)?+
Where is dissakisite-(la) found?+
Is dissakisite-(la) safe to handle?+
What rocks look like dissakisite-(la)?+
What minerals are found with dissakisite-(la)?+
What kind of rock does dissakisite-(la) form in?+
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Find dissakisite-(la) on the map
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