Comparison · Minerals vs Phosphate Minerals
Andalusite vs Lazulite
Andalusite and Lazulite are easy to confuse. Andalusite is harder (Mohs 6.5–7.5) than Lazulite (Mohs 5.75), so Andalusite will scratch Lazulite 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 Andalusite and Lazulite
- Andalusite is harder (Mohs 6.5–7.5) than Lazulite (Mohs 5.75), so Andalusite will scratch Lazulite 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.
- Hold a thin edge to the light: Andalusite is Transparent to translucent, Lazulite is translucent.
- They overlap in green, but Andalusite also comes in brown, red, gray, and pink and Lazulite also comes in blue.
- Well-formed crystals give it away: Andalusite is Orthorhombic, Lazulite is monoclinic.
Andalusite vs Lazulite properties
| Property | Andalusite | Lazulite |
|---|---|---|
| Type | Minerals | Phosphate Minerals |
| Mohs hardness | 6.5–7.5 | 5.75 |
| Luster | Vitreous | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | translucent |
| Specific gravity | 3.13–3.21 | 3.1 |
| Crystal system | Orthorhombic | monoclinic |
| Common colors | Reddish brown, Olive green, Gray, Pink | Blue, Sky blue, Azure blue, Bluish green |
| Rarity | common | rare |
| Typical specimen value | $2–$150+ | $15–$500+ |
Which is more valuable?
Lazulite is usually the more valuable of the two: a typical collector specimen runs about $90 against $20 for Andalusite, and premium Lazulite can reach $500 or more.
About Andalusite
Andalusite is an aluminum silicate, Al2SiO5, and one of three natural polymorphs sharing that exact formula along with kyanite and sillimanite. It crystallizes in the orthorhombic system as stout, nearly square prisms formed under low-pressure, moderate-temperature metamorphism. Its variety chiastolite, which displays a dark cross pattern in cross-section, makes it one of the more recognizable metamorphic minerals to casual collectors.
About Lazulite
Lazulite is a magnesium aluminum phosphate prized by collectors for its rich azure-blue color. It forms hard pyramidal crystals and granular masses, most often in metamorphic quartzites and pegmatites.
Andalusite vs Lazulite FAQ
Is Andalusite the same as Lazulite?
No. Andalusite is a mineral while Lazulite is a phosphate mineral. Andalusite is harder (Mohs 6.5–7.5) than Lazulite (Mohs 5.75), so Andalusite will scratch Lazulite 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 Andalusite from Lazulite?
Andalusite is harder (Mohs 6.5–7.5) than Lazulite (Mohs 5.75), so Andalusite will scratch Lazulite 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. Hold a thin edge to the light: Andalusite is Transparent to translucent, Lazulite is translucent. They overlap in green, but Andalusite also comes in brown, red, gray, and pink and Lazulite also comes in blue.
Which is harder, Andalusite or Lazulite?
Andalusite is harder: Mohs 6.5–7.5 against Mohs 5.75 for Lazulite.
Which is more valuable, Andalusite or Lazulite?
Lazulite is usually the more valuable of the two: a typical collector specimen runs about $90 against $20 for Andalusite, and premium Lazulite can reach $500 or more.
