The Natural Characteristics of Slate

Honister is an ideal site for the extraction of slate because of the effects of glaciation, which, many thousands of years ago exposed three parallel slate veins on both sides of the Gatesgarthdale valley. These are known as the Quey Foot, Honister, and Yewcrag or Kimberley Veins.

Many geologists believe that the slate was originally deposited here as volcanic ash, which settled in water and was then subjected to immense pressures, resulting in a hard, strong and fine grained stone. The process was not continuous, however, and there were periods of inactivity which resulted in sediments being laid down at different rates. This variation accounts for the colour banding and markings that can often be seen in green slate.

Over the countless millennia that followed, geological activity and, in particular, collisions between the Earth's tectonic plates, created great pressures that caused new, flaky materials to build up in the rock at 90 degrees to the direction of the pressure. Slate forms when this pressure is sufficiently constant for large amounts of this flaky material to form in the same plane, a phenomenon which ultimately gives slate its ability to split evenly and consistently, often into very thin sheets.

Honister green slate is thicker and stronger than Welsh slate - in fact, we reckon it's the strongest in the world, with 55 Kg weight to the square metre. Different parts of the site produce different colours, too, so customers can choose from an array of hues, ranging from light sea green to rustic red and a number of very attractive banded varieties.