Technical information
Alta
Rock type: Quartzite slate.
Age: Late Pre-Cambrian (approx. 800 million years).
Alta Slate represents what was originally a homogenous sandstone formation, which was deformed through horizontal movement in the earth’s crust during the formation of mountains in the Caledonian period and metamorphosed into slate.
Its cleavage qualities are defined by regular, smooth layers of flaked micas. Sheet thickness varies between 5 and 30mm.
Workable slate occurs as a 40-200 metre thick zone inside a large "pack" of slatey rocks (the Nalganas layer).
The slate zone is usually horizontal and extends over a large area. Around 30 large and small quarries are currently being worked, and these are divided into three areas (Peska-Langvann, Detsika and Stilla in Skomakerdalen).
The surface structure of the slates varies from a rough and dark grey to a smooth and light grey-green. Polished Alta slate is generally darker than a natural surface.
Alta slate is particularly hard and resistant to wear and is suitable for all product categories.
Product Sheet