The Lady A deposits are underlain by cherty sediments of the Upper Devonian McLaughlin Ridge Formation, Sicker Group. Locally, the sediments strike northwest and dip to the northeast at 50 to 60 degrees.
The Lady A (A zone) deposit is a stratabound taconite deposit composed of grey chert and red jasper hosting bands of very fine grained magnetite with minor specularite. The deposit consists of two lenses which outcrop along strike for a distance of 105 metres, attaining widths of up to 18 metres. An average thickness, determined from drilling, is less than 9 metres. The estimated reserves are 366,000 tonnes with an average grade of 25 per cent iron (Minister of Mines Annual Report 1956, page 135).