Identification guide · Metamorphic Rocks
How to Identify Quartzite
Quartzite is typically white, gray, pink, or reddish, with a vitreous to slightly greasy luster and a white streak, and its hardness of about 7, equal to quartz itself, lets it easily scratch glass and resist a steel knife. It has no true cleavage and breaks with a conchoidal to splintery fracture that cuts directly through the interlocking quartz grains rather than around them. Grain boundaries are often hard to spot without a hand lens, giving the rock a sugary or glassy texture. It is most often confused with quartz-cemented sandstone or with marble, though quartzite scratches glass while marble does not.
Quartzite identification checklist
| Color | White, Gray, Pink, Reddish, Yellow | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to sugary/granular | 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 | 7 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.6–2.7 | Ordinary rock-like heft (specific gravity about 2.6500000000000004), similar to quartz. |
Extra tests for Quartzite
Glass check. Quartzite shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Quartzite look-alikes and how to tell them apart
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Quartzite vs Quartz →
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Quartzite vs Gneiss →
Quartzite is harder (Mohs 7) than Migmatite (Mohs 5–7), so Quartzite will scratch Migmatite 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. Quartzite vs Migmatite →
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Quartzite identification FAQ
How can you tell if a rock is Quartzite?
Check the color (white, gray, pink, and reddish), the vitreous to sugary/granular luster, a Mohs hardness of 7. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Quartzite?
Quartzite has a Mohs hardness of 7. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Quartzite and Quartz?
Quartzite (Mohs 7, vitreous to sugary/granular luster) and Quartz (Mohs 7, vitreous, greasy on fracture surfaces luster) look alike, but hardness, streak and heft usually separate them. See the full Quartzite vs Quartz comparison for a side-by-side table.
Is Quartzite worth anything?
Entry-level Quartzite 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 Quartzite?
Quartzite is most often white, gray, pink, and reddish. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
