Rock · Metamorphic rock
Gneiss
A rock is a mix of minerals, so it has no single hardness or streak. Scratching it tests whichever grain you happen to touch. Stoneye names the rock from the photo and lets you test the minerals inside it.
Minerals in it
- QuartzHardness (Mohs) 7
- OrthoclaseHardness (Mohs) 6–6.5
- MicroclineHardness (Mohs) 6–6.5
- PlagioclaseHardness (Mohs) 6–6.5
- BiotiteHardness (Mohs) 2.5–3
- MuscoviteHardness (Mohs) 2–2.5
- AlmandineHardness (Mohs) 7–7.5