The Smith Island occurrence limestone quarry is located on the north side of Tsum Tsadai Inlet on Smith Island, approximately 18 kilometres south of Prince Rupert.

A limestone band at least 30 metres wide enclosed in Permian-Triassic biotite-muscovite schists follows the north shore of Tsum Tsadai Inlet on the west side of Smith Island for 1.0 kilometre. The bed strikes 050 degrees and dips 53 degrees northeast.

The deposit is comprised of bluish white, coarse-grained limestone that becomes interbedded with schist along the margins of the band. The deposit is frequently contaminated with thin beds of highly siliceous limestone and calcareous quartzite. Some brown mica, white tremolite and pyrite are also present in the limestone. A sample of the purer limestone contained 54.64 per cent CaO, 0.38 per cent MgO, 0.98 per cent SiO2, 0.11 per cent Al2O3, 0.08 per cent Fe2O3 and nil sulphur (Canada Bureau of Mines Report 811, page 176, Sample 39).

An extension of the band outcrops 1.5 kilometres to the east and continues along the north shore of the inlet for 2.5 kilometres. A quarry was opened on this part of the deposit in 1950 by Columbia Cellulose Company. The quarry was abandoned in 1952 because of the impurities in the limestone. Total production between 1950 and 1952 amounted to 9459 tonnes.

In 2016, Durango Resources Inc. currently holds the past-producing Smith Island limestone project and completed a small sampling program on the Smith Island and Mayner's Fortune (103I 113) properties. A total of 24 samples were taken on the properties and submitted for assay.