Dumortierite Quartz is a popular lapidary material characterized by dense inclusions of fibrous blue dumortierite needles trapped within a clear or milky quartz host. It is easily identified by its distinctive denim-blue color and typical massive habit, making it a favorite for carving and jewelry.
Is this dumortierite quartz?
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 dumortierite quartz with a known reference. Dumortierite Quartz sits at Mohs 7, 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: blue, violet-blue, deep blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Dumortierite Quartz vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Dumortierite Quartz is noticeably harder (Mohs 7 vs. 5.5-6).
How to tell apart: Dumortierite Quartz is noticeably harder (Mohs 7 vs. 5-5.5); streak differs, so Dumortierite Quartz leaves white, Lapis Lazuli leaves light blue; luster reads vitreous on Dumortierite Quartz and dull to vitreous on Lapis Lazuli.
How to tell apart: Luster reads vitreous on Dumortierite Quartz and waxy on Blue Chalcedony.
Often found alongside dumortierite quartz
Minerals reported to co-occur with dumortierite quartz. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.65 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- hydrothermal veins and pegmatites
Where rockhounds find dumortierite quartz
Classic worldwide localities
- Namibia
- Brazil
- Madagascar
- USA
- Peru
Field-hunting tip
Where it forms: hydrothermal veins and pegmatites. If you start seeing quartz, dumortierite, muscovite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find dumortierite quartz on the map
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