Rock is classified into three basic groups:⭐IGNEOUS⭐SEDIMENTARY ⭐METAMORPHICIt is desirable to know something about schoolboy geology when you are in the screening business.Igneous The word igneous means fire and is the oldest form of the earths development. Some of the more common igneous stone are granite, basalt, gabbro and lava. Without going into any detail about igneous stone some generalisations can be made. Igneous stone came from the solidification of hot, molten lava that ...