The Giscome Ballast area is underlain by Lower Mississippian to Permian basalt of the Slide Mountain Complex.

The Canadian National Railway depleted one railroad ballast quarry near Giscome and followed in 1983 by starting production from a new quarry about 2 kilometres west of the old one (Exploration in BC 1983).

In 2007, UMA Engineering Ltd. (UMA) conducted a site investigation for Canadian National Railway (CN) on Mineral Claim 555303 located north of the current CN Giscome quarry and west of Eaglet Lake. The scope of work included geological mapping of the bedrock outcrops to determine if the rock is suitable for producing railway ballast. The report indicated that the quarry had begun production in 1983 and had produced approximately 3,200,000 tonnes of ballast (Assessment Report 29783).

Significant production is known to have occurred in 1999, 2001 and 2005 and in some years since 1983 no production occurred at all.