Some commonly used types of stone are:

Limestone

Limestone is the most abundant of the sedimentary rocks and is produced from the mineral calcite (calcium carbonate) and sediment. The main source of limestone is the limy ooze formed in the ocean.
This stone is abundant in Ireland's Southeast and is the predominant stone in much of Kilkenny and Waterford.
Ideal for use in dry or pointed walls Limestone can also be worked to produce 'cut' pillars, cills and all kinds of stone features.

Granite

Granite is a light-colored , coarse-grained igneous rock formed by cooling of silica-rich magma below the surface of the earth. It is called granite because of the granular surface. Granite is frequently used for buildings and monuments.
Granite is a very hard and durable stone and can average over 350 to 400 million years old and range in colour from black, grey, pale to dark pink, yellow to vibrant red.

Sandstone

Sandstone is a sedimentary rock that forms from the cementing together of sand sized grains forming a solid rock. Quartz is the most abundant mineral that forms sandstone. The presence of other minerals in the stone produces a variety of colours and textures that are very attractive.
Often used in the facing of modern structures Sandstone has also been used to form very ornate building features.
The stone is easily cut and walls or pillars can be created with a very uniform size stone or with a more random look

Local Fieldstone

Local fieldstone is stone that is collected from local land. It can be hard to come by, but especially in a country setting, it is well worth the effort as it can make a wall look instantly aged and blends beautifully into the landscape.
Fieldstone can often be reclaimed from demolished old buildings and ditches or with the landowners permission, can be collected from certain large areas of farm land.