Shale is exposed in a railway cut between the United Empire Colliery (092HSE218) and an old cement plant on Allison (One Mile) Creek (092HSE169), about 4 kilometres northeast of Princeton.
The deposit is situated at the eastern margin of the Princeton Basin, a northerly striking fault-bounded trough filled by Eocene volcanic rocks of mainly intermediate composition, comprising the Lower Volcanic Formation, and an overlying Eocene sedimentary sequence of sandstone, shale, waterlain rhyolite tephra (tuff) and coal, up to 2000 metres thick, comprising the Allenby Formation. The bed is hosted in a sequence of white-weathering sandstone, minor siltstone and rare shale, known informally as the Hardwick sandstone, in the Allenby Formation (Princeton Group) (Open File 1987-19). The strata dips south in the railway cut.
The shale is moderately soft and cracks badly on drying, after being mixed with water to form a plastic mass. Air shrinkage is quite high, at 13.6 per cent (Geological Survey of Canada Memoir 65, page 24). The stickiness and excessive air shrinkage of the shale (clay) is reduced after preheating to 300 degrees Celsius. The firing characteristics of the preheated clay are as follows (Geological Survey of Canada Memoir 65, page 24):
Cone Fire shrinkage Absorption Colour
(per cent) (per cent)
010 1 17.10 Dark pink
05 3.3 10.2 Dark pink
1 7 6.10 Dark brown
The material is steel hard at cone 1 and nearly so at cone 010.
Firing characteristics of a mixture of 75 per cent calcined clay and 25 per cent raw clay are as follows (Geological Survey of Canada Memoir 65, page 26):
Cone Fire shrinkage Absorption
010 1.85 16.58
05 2.4 11.76
1 6.6 4.92
The clay burned to a salmon colour up to cone 010, and a dark red colour from cone 05 to 1. It was nearly steel hard at cone 010 and completely so at cone 05. This material is not considered to be a fireclay. It may be used for red brick, but if used alone it has to be preheated.
The upper part of the shale bed is reported to have been utilized for making common brick, after mixing with surface soil, some time before 1915. The brick was however found to be rather porous (Geological Survey of Canada Memoir 65, page 22) .