You picked up an interesting rock on a hike or a beach and now it is sitting on the windowsill, unidentified. Rocks and minerals take a little more detective work than a flower, but a handful of properties will get you close — and a photo will get you the rest of the way.
Rock or Mineral?
A mineral is a single naturally occurring substance with a consistent makeup (quartz, calcite, pyrite). A rock is a mixture of minerals (granite, sandstone, basalt). Knowing which you are holding shapes everything else you check.
The Properties That Matter
- Color — a starting point, but unreliable alone since impurities change it
- Luster — does it look metallic, glassy, pearly, or dull?
- Hardness — can it be scratched by a fingernail, a coin, or steel? (the Mohs scale)
- Shape and crystal form — cubes, six-sided crystals, layers, or rounded grains
- Streak — the color of the powder it leaves on an unglazed tile
- Feel and weight — is it unusually heavy, grainy, or smooth?
Where You Found It Is a Clue
Riverbeds tumble stones smooth; volcanic areas produce basalt and obsidian; limestone regions hide fossils and calcite. The landscape narrows the possibilities before you test a thing.
Snap a Photo for an Instant Read
Spotter identifies rocks, minerals, crystals, gemstones, and fossils from a photo, with detail on how they form and where they occur. It is the same app that handles the plants, animals, and fungi you pass on the trail — so the interesting rock, the wildflower next to it, and the bird overhead all get identified in one place.
Try Spotter Free on iOS & Android
Plants, animals, fungi, and rocks — all from a photo. 5 free identifications every day, no credit card required.
Run through color, luster, hardness, and shape, factor in where you found it, and you will have a solid guess. A photo confirms it — and tells you the story of how that rock came to be.