The West pipe underwent yet a third phase of brecciation which resulted in a rubble breccia of carbonate and clastic sediment clasts in a rock flour matrix. This unit is termed a sediment clast breccia and is easily recognized by the extensive pyrite replacement of the carbonate clasts. Ore Mineralization and Alteration Mineralization consists predominantly of free gold particles generally less than 20 microns in diameter. The gold occurs as coatings and fracture fillings and as encapsulated grains within pyrite suggesting at least two periods of precious metal mineralization. Galena, chalcopyrite, and sphalerite have been reported in minor amounts.
Pyrite occurs in three distinct styles.
Vein or fracture controlled pyrite occurs as massive, euhedral aggregates of crystals filling open spaces between breccia clasts and as finer grained films on fracture surfaces. Replacement pyrite is most common in the sediment clast breccias where carbonate clasts, in particular, have undergone partial to total replacement by pyrite. Alteration consists of near surface oxidation, significant sericitization and moderate argillization. Quartz is an abundant gangue mineral commonly occurring as veinlets and with pyrite as replacements of sediment clasts. Adularia is present and may be locally abundant.