Identification guide · Igneous Rocks
How to Identify Kimberlite
Kimberlite is typically a dark greenish-gray to bluish rock with an altered, weathered surface and a mixed texture of rounded olivine grains, mica flakes, and rock fragments in a fine-grained groundmass. Its luster varies by mineral, its streak runs gray to greenish, and its hardness is hard to pin down since it is a heterogeneous mixture, not a single mineral. Fresh kimberlite weathers fast to a soft clay called blue ground, so it is most reliably confirmed by its indicator minerals rather than appearance alone.
Kimberlite identification checklist
| Color | Blue-gray ('blue ground'), Yellow ('yellow ground', weathered), Dark green, Gray | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Dull to vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 5–6.5 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Fracture | Uneven | |
| Specific gravity | 2.5–2.9 | Ordinary rock-like heft (specific gravity about 2.7), similar to quartz. |
Kimberlite look-alikes and how to tell them apart
Both sit near Mohs 5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Kimberlite vs Feldspar →
Quartz is harder (Mohs 7) than Kimberlite (Mohs 5–6.5), so Quartz will scratch Kimberlite 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. Kimberlite vs Quartz →
Both sit near Mohs 5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Kimberlite vs Andesite →
Both sit near Mohs 5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Kimberlite identification FAQ
How can you tell if a rock is Kimberlite?
Check the color (blue-gray ('blue ground'), yellow ('yellow ground', weathered), dark green, and gray), the dull to vitreous luster, a Mohs hardness of 5–6.5. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Kimberlite?
Kimberlite has a Mohs hardness of 5–6.5. 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 Kimberlite and Feldspar?
Kimberlite (Mohs 5–6.5, dull to vitreous luster) and Feldspar (Mohs 6–6.5, vitreous to pearly luster) look alike, but hardness, streak and heft usually separate them. See the full Kimberlite vs Feldspar comparison for a side-by-side table.
Is Kimberlite worth anything?
Entry-level Kimberlite specimens sell for around $1, typical collector pieces about $10, and premium examples $75 or more depending on size, quality and locality.
What color is Kimberlite?
Kimberlite is most often blue-gray ('blue ground'), yellow ('yellow ground', weathered), dark green, and gray. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
