A photo helps, and the checks in what type of rock is this help more. This page covers flint, the beach stone with the clearest signs, and a few rock types to compare it with. If you would rather have a suggestion from a photo, try LithoCanvas.
Flint
Flint is a form of quartz that forms in chalk and limestone. Inside a nodule it is usually dark grey or black, green, white or brown, with a glassy or waxy look. A thin crust on the outside is commonly white and rough. When struck, flint breaks into thin, sharp flakes. It is very durable and can throw sparks. On Rügen in Germany, the pebble beach at Cape Arkona is made of flint eroded from the chalk cliffs. Flint from England's south coast can contain fossil marine life such as coral fragments.
Granite, gneiss, sandstone, limestone
Granite is an igneous rock with visible crystals that grew slowly at depth. Gneiss is metamorphic, with bands of lighter and darker layers. Sandstone and limestone are sedimentary, and sandstone shows visible sand grains. Layers and fossils point to a sedimentary rock. Look at grain and banding on each find.
Special finds
- A stone with a natural hole: hag stones.
- A light, warm, yellowish piece: how to tell if amber is real.
Collecting
Rules on taking stones depend on the country and on protected areas. Check locally.
When you are unsure
LithoCanvas is an Android app by Senorit that suggests what a photo shows. The result is a suggestion, not a verdict, and your photo goes to Google Gemini only if you agree. The app gives neither authenticity nor value.
Questions and answers
How do I identify flint?
A glassy or waxy inside, often dark, a white rough crust outside, and sharp flakes where it breaks.
What other rocks can I compare it with?
Granite (igneous), gneiss (metamorphic), sandstone and limestone (sedimentary) are useful reference types.
How do I identify a beach rock?
Check grain, colour, hardness and streak. The steps are in what type of rock is this.