Rock type: Feldspar metasandstone. 
Age: Silurian-Devonian (approx. 650 million years).
The depositing of sediments formed the Offerdal highland region during a period of continental settling. During the formation of the Caledonian mountain range the sediment was moved, deformed and metamorphosed into the Offerdal region as you see it today.
Offerdal slate is a part of the Offerdal highland region and has a fine-banded structure or cleavability. This cleavability can be characterised by clear quartz and feldspar-rich bands together with a cleavage plane rich in mica. The rock’s cleavability makes it possible to split the slates to a thickness of just 5 mm. 
The surface is rippled and grey in colour. Polished surfaces vary between grey and green. Offerdal slate is hard and is a quite unique building stone. It occurs in an approx. 10m thick zone over a broad area of the Offerdal region. 

Quarrying activities are concentrated in the north-west area of Krokoms Municipality, J?mtland County, in Sweden.

Petrografi c analysis
Density 2740 kg/m3 NS-EN 1936
Water absorption 0,1 % by weight NS-EN 13755
Flexural strength 35,1 MPa NS-EN 12372
Abrasion resistance 18,0 mm NS-EN 14157(A)
Slip resistance 77 SRV, dry NS-EN 14231
19 SRV, wet
Mineralogy
Quartz 44 %
Mica 33 %
Feldspar 23 %