Limestone of the Middle Triassic Brooklyn Formation outcrops north of the Marguerite mine, 2 kilometres due north of Deadwood, 3 kilometres northwest of Greenwood. The mass trends northward for 1500 metres with a width of up to 800 metres. The Greyhound Creek fault truncates the limestone to the east. Underlying conglomerate of the Brooklyn Formation outcrops to the west. A few north-northeast trending syenite and quartz monzonite dykes intrude the limestone deposit near its south end.
The limestone is massive, medium to fine grained and grey to white in colour. An intricate network of white calcite veinlets cuts the rock. Rounded, light to dark grey chert nodules and thin beds of cherty "jasperoid" are sometimes present. Two samples of limestone from the Marguerite Mine analyzed as follows (Geological Survey of Canada Memoir 19, p. 19, Samples 1, 3):
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Sample CaO CaCO3 MgCO3 Insolubles Al2O3+Fe2O3 Undetermined
1 53.71 95.86 1.36 0.32 0.10 2.46
3 54.72 97.67 1.40 0.40 0.20 0.33
Sample 1 is of white, crystalline limestone and while Sample 3 is of grey, crystalline limestone.
This limestone was burnt in a kiln located 50 metres northeast of the entrance of the mine in the early part of this century. No production figures are available.
