Comparison · Minerals vs Semi-Precious Stones
Dumortierite vs Lapis Lazuli
Dumortierite and Lapis Lazuli are easy to confuse. Dumortierite is harder (Mohs 7–8.5) than Lapis Lazuli (Mohs 5.5), so Dumortierite will scratch Lapis Lazuli and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Dumortierite and Lapis Lazuli
- Dumortierite is harder (Mohs 7–8.5) than Lapis Lazuli (Mohs 5.5), so Dumortierite will scratch Lapis Lazuli and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
- Streak color differs: Dumortierite leaves a white streak on unglazed porcelain, Lapis Lazuli leaves light blue.
- Dumortierite feels noticeably heavier for its size (specific gravity 3.3–3.4 versus 2.8 for Lapis Lazuli).
- Hold a thin edge to the light: Dumortierite is Translucent to opaque, Lapis Lazuli is opaque.
- They overlap in blue, but Dumortierite also comes in purple, brown, and pink and Lapis Lazuli also comes in yellow.
- Well-formed crystals give it away: Dumortierite is Orthorhombic, Lapis Lazuli is cubic.
Dumortierite vs Lapis Lazuli properties
| Property | Dumortierite | Lapis Lazuli |
|---|---|---|
| Type | Minerals | Semi-Precious Stones |
| Mohs hardness | 7–8.5 | 5.5 |
| Luster | Vitreous, silky when fibrous | vitreous |
| Streak | White | Light blue |
| Transparency | Translucent to opaque | opaque |
| Specific gravity | 3.3–3.4 | 2.8 |
| Crystal system | Orthorhombic | cubic |
| Common colors | Blue, Violet-blue, Brownish, Pink (rare) | Deep Blue, Blue, Blue with gold flecks |
| Rarity | common | uncommon |
| Typical specimen value | $2–$150+ | $10–$500+ |
Which is more valuable?
Lapis Lazuli is usually the more valuable of the two: a typical collector specimen runs about $50 against $20 for Dumortierite, and premium Lapis Lazuli can reach $500 or more.
About Dumortierite
Dumortierite is an aluminum borosilicate mineral crystallizing in the orthorhombic system, best known for its intense blue to violet-blue color caused by trace iron and titanium substitutions. It typically forms fibrous, needle-like crystal aggregates within metamorphic rocks rich in aluminum, such as schists and gneisses subjected to high temperature and pressure. Its deep, saturated blue color has made it a popular but often misidentified substitute for lapis lazuli and sodalite in ornamental carvings.
About Lapis Lazuli
Lapis lazuli is a deep blue metamorphic rock prized since antiquity. The golden flecks are pyrite inclusions, while the blue comes from lazurite.
Dumortierite vs Lapis Lazuli FAQ
Is Dumortierite the same as Lapis Lazuli?
No. Dumortierite is a mineral while Lapis Lazuli is a semi-precious stone. Dumortierite is harder (Mohs 7–8.5) than Lapis Lazuli (Mohs 5.5), so Dumortierite will scratch Lapis Lazuli and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
How can you tell Dumortierite from Lapis Lazuli?
Dumortierite is harder (Mohs 7–8.5) than Lapis Lazuli (Mohs 5.5), so Dumortierite will scratch Lapis Lazuli and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Streak color differs: Dumortierite leaves a white streak on unglazed porcelain, Lapis Lazuli leaves light blue. Dumortierite feels noticeably heavier for its size (specific gravity 3.3–3.4 versus 2.8 for Lapis Lazuli).
Which is harder, Dumortierite or Lapis Lazuli?
Dumortierite is harder: Mohs 7–8.5 against Mohs 5.5 for Lapis Lazuli.
Which is more valuable, Dumortierite or Lapis Lazuli?
Lapis Lazuli is usually the more valuable of the two: a typical collector specimen runs about $50 against $20 for Dumortierite, and premium Lapis Lazuli can reach $500 or more.
