Fundamental though minerals are, more noticeable in many vineyard soils are the larger stony pieces: the rigid, solid aggregates of minerals termed rock. Rocks are classified into three groups according to their origin.
Igneous rocks are solidified from a melt. Lava chills at the Earth’s surface to form rocks such as basalt, often with associated volcanic products such as tuff. Molten material at depth tries to move upwards, progressively cooling until the mass finally solidifies while still deep underground, forming a plutonic igneous rock which may eventually be exposed at the surface by erosion of the overlying rocks. granite is the most widespread plutonic igneous rock in vineyards.
