Slate of finished and unfinished slate has increased. It has slate in various colors. Deposits of slate exist throughout the Australian continent, with large reserves quarried in the Adelaide Hills (Willunga and Kanmantoo) and the Mid North (Mintaro and Spalding). Because slate was formed in low heat and pressure, compared to a number of other metamorphic rocks, some fossils can be found in slate; sometimes even microscopic remains of delicate organisms can be found in slate. Slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional
Slate industry in Spain has led to the region’s unique geological development in respect of slate. Slate deposits are over 500 million years old, having been formed during the Cambrian, Ordovician and Silurian periods of the Palaeozoic era. Essentially, slate forms when the clay minerals in shale are put under increased pressure with high temperatures. The clay starts to revert to the mica minerals which cause the rock to grow hard with pronounced cleavage) directions. It is this cleavage which enables slate to be broken along flat, even planes. A large variety of colours and textures of slate can be produced, and the final