The Ayrshire countryside southwest of Glasgow is some of the most attractive and scenic countryside in southern Scotland.

Within this area basaltic and andesitic agate bearing rocks from the Old Red Sandstone (ORS) of the Devonian Period, about 380 million years old, comprise two main outcrops abutting the coast at Dunure and Turnberry/Maidens. These lava outcrops have been well surveyed and are clearly demarcated on the above geological map of Scotland. It is believed that the ORS lavas found near the coast also extend under the sea, but the size and extent of these structures is largely unknown. It is certainly the case that agates, many of which are very waterworn, are found well outside the seaward boundaries of the lava fields.

The ORS andesitic lava is also found stretching inland along the line of the Southern Upland Fault near Straiton, Dalmellington and New Cumnock and northeast towards Edinburgh. With some exceptions, agates that have been found in these areas are generally of a poorer quality than in the coastal localities. Many of the ORS areas to the northeast also mainly lie in grass-covered uplands that have not as yet been fully explored. A smaller subsidiary area of ORS andesite also occurs inland to the east of Kilmarnock near Galston. This is the site of the famous Burn Anne agate locality.

Ayrshire has produced a huge amount of agate over the years and collecting was particularly widespread in the 1970s and 1980s. This led to the depletion of certain sites although, as always, the keen collector manages to find plenty of possibilities if he or she is prepared to persevere.