Glendyne's opencut deposit is located along a dark grey slate bed that is part of a vast mineral assemblage of grey slate, dark grey siltstone, and quartzite found in the Temiscouata Formation (Devonian –400 to –350 million years).
During the Appalachian orogeny, these sedimentary rocks were distorted into large folds and acquired fissility. Fissility is as regular as the minerals are fine.
Slate found at Glendyne's quarry is dark grey with a tone of blue. Its colour is very homogeneous despite the presence of a light stratification marked by silty beds which, often of very fine nature, do not affect slate schistosity.
Due to the Nordic climate, surface alteration is very low. The deposit was preserved from meteorological alterations typical of temperate and hot climates. The Glendyne quarry is thus proud to produce stones of very high quality.