The Clear Hills Deposit is an oolitic ironstone deposit that is best classified as Minette type iron formation. The most prominent feature of these oolitic ironstones is the presence and abundance of oolites and pisolites composed of goethite and nontronite that were deposited in shallow water environments, close to shorelines or abandoned deltas.
The ironstone deposit consists of ooliths, siderite and phosphate clasts, in a clastic matrix with silica cement. The ooids are composed of fine concentric laminae of goethite, nontronite (an iron rich smectite) and amorphous phosphate phase in variable amounts. The cores of the ooids are variable as well and consist of quartz, feldspar, phosphate, magnetite/hematite, broken pieces of older ooids and other clastic fragments. The ooids are set in a fine- grained iron-rich clastic matrix primarily composed of an amorphous silica cement described as “ferruginous opal” that contains 24 weight percent (“wt%”) Fe. Goethite containing 46 to 56 wt% Fe is the primary iron mineral of interest in this deposit.
Oolitic ironstones typically contain between 30 and 50 wt % Fe. Oolitic iron formations are, however, much more aluminous and contain high concentrations of phosphorus P (an average of 0.5 to 1 wt %) than banded non-oolitic iron formations. The SiO2 content is usually greater than 20 wt %.
The deposit is bedded, flat lying, and has an average thickness of 8.3 m and a maximum thickness of 15 m. The deposit ........