Late in the summer of 1963, a large nephrite boulder was found on the roadside where a culvert had been built for Seywerd Creek beneath the Cassiar-Stewart highway (Highway 37). The creek flows into Dease Lake at Sawmill Point, near the lakes north end. Nephrite (jade) boulders were found in considerable quantity along the creek for more than 1.6 kilometres east of the road.
Rocks exposed along the creek are dominantly argillites and greywackes of the Mississippian-Triassic Kedahda Formation (Cache Creek Complex). There are also outcrops of Cache Creek Complex serpentinite a short distance south of the creek, which are upper Mississippian-Permian age.
Numerous nephrite boulders, some up to 4.5 tonnes in weight, have been found in the creek. Quality of the material in most instances is difficult to judge from the exposed surfaces, so as a consequence each boulder is initially sampled by breaking a slab along a sawcut 15 to 25 centimetres deep made with a portable diamond saw. Although some nephrite is sheared, and some have inclusions of magnetite or is mottled, some material of very good colour has been found (Minister of Mines Annual Report 1965, page 250).
In 1965, a number of boulders were cut into slabs and shipped; about 1.8 tonnes of jade were sold in West Germany and about 3.1 tonnes in Japan. In 2006, prospecting was conducted on behalf of Dynasty Jade Ltd. following up local stories of exposed jade boulders in creeks. The two major creeks explored were Saw Mill Creek and Dorthy Creek.