Identification guide · Phosphate Minerals
How to Identify Lazulite
Lazulite is usually blue, sky blue, and azure blue with a vitreous luster and is translucent. It has a Mohs hardness of 5.75. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Its streak is white. It is most often confused with Kyanite, Andalusite, and Labradorite; the tests below separate them.
Lazulite identification checklist
| Color | Blue, Sky blue, Azure blue, Bluish green | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 5.75 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Indistinct | |
| Fracture | Uneven to splintery | |
| Specific gravity | 3.1 | Heavier than it looks (specific gravity about 3.1). |
| Crystal system | Monoclinic |
Lazulite look-alikes and how to tell them apart
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Lazulite vs Kyanite →
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. Lazulite vs Andalusite →
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Lazulite vs Labradorite →
Both sit near Mohs 5.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for a hard, azure to sky-blue mineral forming sharp pyramidal crystals or granular masses.
- Lazulite is notably harder than azurite and can show strong color change with viewing direction.
- Distinguish it from lazurite and sodalite by its greater hardness and its occurrence in quartzite and pegmatite.
Lazulite identification FAQ
How can you tell if a rock is Lazulite?
Check the color (blue, sky blue, azure blue, and bluish green), the vitreous luster, a Mohs hardness of 5.75 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Lazulite?
Lazulite has a Mohs hardness of 5.75. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is the difference between Lazulite and Kyanite?
Lazulite (Mohs 5.75, vitreous luster) and Kyanite (Mohs 5, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Lazulite vs Kyanite comparison for a side-by-side table.
Is Lazulite worth anything?
Entry-level Lazulite specimens sell for around $15, typical collector pieces about $90, and premium examples $500 or more depending on size, quality and locality.
What color is Lazulite?
Lazulite is most often blue, sky blue, azure blue, and bluish green. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
