For thousands of years, people have depended on stone. During the Stone Age, most people depended on stone completely for hear, shelter and hunting animals. The main stone they used was flint. With flint they could start a fire easily and make very sharp arrow or spear heads for hunting. Flint is usually dark grey, black, and green, white, or brown in colour and usually quite small when found. Flint is a hard form of form of the mineral quartz. It was used as spears and arrows because it could be sharpened easily by cutting thin slivers off it and because it is a very hard stone. Flint has been used as a building material for thousands of years also, it was used to build the Burgh Castle in Norfolk and it is still used to the present day. Flint is common in most areas in Ireland.