11. The argillite probably formed from volcanic ash falls. 12. The deposits are hosted in shear zones in argillite of the Precambrian Belt Supergroup. 13. This technique lends stability to the fragile argillite . 14. Rocks on North Solitary Island consist of mudstone and a light green brittle sillicaceous argillite . 15. The rock types are; vitreous quartzite, sericitic quartzite, and siltite-argillite . 16. The impermeability of argillite is primarily to blame for Sourland Mountain s extremely poor aquifer. 17. For the Haida, argillite was perhaps part of a movement towards greater financial gain. 18. Prior to 1820 there were no argillite carvings found in any public or private collections. 19. There is also Precambrian sedimentary argillite , dating back to 1.7 billion years ago. 20. In the Skidegate dialect of the Haida language argillite is called " kwawhlhal ".
