Silver Islet, Sibley Township, Thunder Bay District, Ontario, Canadai

Regional Level Types
Silver Islet	- not defined -
Sibley Township	Township
Thunder Bay District	District
Ontario	Province
Canada	Country

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Silver Islet was named in 1868 by Thomas Macfarlane, who had been engaged to survey silver prospects on claims of the Montreal Mining Company in the vicinity. The islet was about 25 m in diameter and barely rose above the surface of the lake; relatively little wind was required for waves to wash completely over the rock. As recounted in Wilson (1986), once sampling had indicated that the deposit warranted development, engineer William Frue exerted considerable effort over the next several years to build and maintain an extensive breakwater--essentially a whole new island--around the natural outcrop to defend the mine's infrastructure from Lake Superior's legendary winter storms.

Two bonanzas of silver ore were found which kept the mine in operation into the early 1880s, the original near-surface discovery and another large ore body struck in 1878. An inclined shaft served 15 levels in the mine. Exploration ultimately reached a depth of 388 m without locating further paying ore. The end came in 1883 when the steamer that was to deliver the mine's winter supply of coal for pumping water out of the mine became stranded by ice and could not make the delivery. Fuel ran out in March of 1884, the mine flooded, and the company's directors called it quits. An historical marker at the town of Silver Islet on the mainland states that in its 16 years of operation the mine produced $3.25 million in silver.

The property was partly dewatered and re-examined in the 1920s, and the extensive dumps surrounding the once-again bare islet have been sampled periodically by divers, but so far the property has seen no development or production since 1883.

According to Wilson (1986), "[t]he general geology of Silver Islet is quite simple. Precambrian Animikie sediments form the country rock of the area. Cutting through these sediments is a large diabase dike of Keweenawan age. Cutting the dike at a right angle is a heavily brecciated fault zone. Vein material cementing the fissures and fault breccia at this crossing contains silver." Vein deposits at Silver Islet have been characterized as "primary" and "secondary". The primary deposits, which account for 90% or more of the total vein volume, consist of fine-grained and uniform mixtures of dolomite, quartz, and a range of metalliferous minerals. Secondary vein deposits, encountered mostly within about 200 m of the surface, "consist of discontinuous replacement bodies, veins, and vug linings" and contain a wide range of mineral textures "including wires, leaves, and nuggets of silver and well-formed crystals of other minerals."

Map coordinates are for the shafts visible on Google Earth imagery. See also the "Silver Islet mine" locality page.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.

Mineral List

Mineral list contains entries from the region specified including sub-localities

28 valid minerals.