Identification guide · Silicate Minerals
How to Identify Zoisite
Zoisite is usually green, pink, and blue with a vitreous luster and is transparent. It has a Mohs hardness of 6.5. It scratches glass and a steel knife and cannot be scratched by a steel file. Its streak is white. It is most often confused with Calcite, Microcline, and Quartz; the tests below separate them.
Zoisite identification checklist
| Color | Green, Pink, Blue, Gray | 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 | Transparent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6.5 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect | |
| Fracture | Uneven | |
| Specific gravity | 3.3 | Heavier than it looks (specific gravity about 3.3). |
| Crystal system | Orthorhombic |
Zoisite look-alikes and how to tell them apart
Zoisite is harder (Mohs 6.5) than Calcite (Mohs 3), so Zoisite will scratch Calcite and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Zoisite vs Calcite →
Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Zoisite vs Microcline →
Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Zoisite vs Quartz →
Zoisite is harder (Mohs 6.5) than Tremolite (Mohs 5.5), so Zoisite will scratch Tremolite 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.
Field tips
- Look for striated prismatic crystals or massive aggregates with one direction of perfect cleavage.
- Hardness near 6.5 and strong pleochroism in gem material help distinguish zoisite.
- Association with epidote and metamorphic host rocks supports identification.
Zoisite identification FAQ
How can you tell if a rock is Zoisite?
Check the color (green, pink, blue, and gray), the vitreous luster, a Mohs hardness of 6.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Zoisite?
Zoisite has a Mohs hardness of 6.5. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Zoisite and Calcite?
Zoisite (Mohs 6.5, vitreous luster) and Calcite (Mohs 3, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Zoisite vs Calcite comparison for a side-by-side table.
Is Zoisite worth anything?
Entry-level Zoisite specimens sell for around $12, typical collector pieces about $70, and premium examples $450 or more depending on size, quality and locality.
What color is Zoisite?
Zoisite is most often green, pink, blue, and gray. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
