Rock type: Quartzite slate. 
Age: Late Pre-Cambrian (approx. 750 million years).
Oppdal 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 10 and 60mm. 
Workable slate occurs in several parallel zones, each of which can be up to 20 metres thick. The lower zones consist of light to mid-grey Oppdal slates. Dark Oppdal slate and Golan occur in the upper regions. 
The slate is somewhat more porous than, for example Alta slate, and occurs in thicker strata. On the other hand, Oppdal slate can be easily scored and cut, and it is therefore well suited for use in walls and products with unfinished edges. 
The surface and colour of unfinished slate varies somewhat with this rock type, and when polished the colours and patterns can vary a great deal.
Petrografi c analysis
Density NS-EN 1936 2710 kg/m3
Water absorption NS-EN 13755 0,2 % by weight
Flexural strength NS-EN 12372 22,1 MPa
Abrasion resistance NS-EN 14157(A) 20,0 mm
Slip resistance NS-EN 1423169 SRV, dry
29 SRV, wet
Comment
Frost resistant
Mid-value natural riven after 48 frost/defrost cycles
Tested on honed C600. Method A: Wide Wheel abrasion test, Capon.
Honed C600
Honed C600