The Tash limestone occurrence is located on the Tashish River, approximately 12 kilometres from its mouth.

The area is underlain by limestone of the Upper Triassic Quatsino Formation.

Locally, the limestone is fine- grained tan through grey marble that can be massive or brecciated. The brecciated variety is cut by a random network of white carbonate veinlets and stringers to 1 centimetre. A grey-black limestone cut by sub-parallel white carbonate veinlets (to 7 millimetres) also occurs.

In 1991 and 1992, Mammoth Geological Ltd. performed geological mapping and geochemical sampling to identify areas of limestone or marble for potential use as both tiles and face finished slab. In 1993, at least one potential quarry site had been identified in a dark brown to grey black marble.