List of stones

Brimstone is an old English biblical name for sulfur. Brimstone gets its name because it is formed around the vents of volcanoes.

Chalk is a soft, white rock that can be used to draw with on rough surfaces. Chalk is usually sold in small coloured sticks, for drawing on blackboards and sidewalks.

A crystal is any solid that is made up of tiny parts called molecules, aranged in a regular geometric pattern in all three dimensions. Many rocks are crystalline, and can be very pretty. The crystals in the picture are salt crystals.

Emeralds are a gemstone quality variant of beryl, made from beryllium aluminium silicate. The deep green colour is from trace amounts of chromium. Emerald tends to be imperfect, with inclusions and fissures so while the pure stone is hard, emeralds are actually quite prone to breaking.

When an animal or plant dies and is buried under the ground with the right conditions for thousands or even millions of years, it turns to stone. Later when we dig them back up, we call them a fossil. When something has been turned into a fossil it is fossilised. People have found fossils of all sized creatures, from tiny sea snails, to frogs, right up to enormous dinosaurs. Most of the creatures that people find as fossils are extinct - you can no longer see a living animal of that kind. The fossil in the picture is a trilobite.