Reopening of the Miller Lake-O'Brien mine in the Gowganda District, Ontario by the Siscoe Gold Mines, Ltd. offered opportunity to collect samples representative of the richer silver ores and to submit them to paragenetic studies. Special interest centers upon (1) the small number of abundant minerals in the ores, (2) the deposition of much native silver with calcite along fractures, (3) direct replacement of fairly fresh as well as highly altered diabase by native silver, (4) the abundance of silver dendrites as automorphic replacements of calcitized diabase, (5) widespread replacement of silver dendrites late in the primary mineralization by calcite, (6) a scarcity of sulphur-bearing minerals in the ores, suggesting that a paucity of sulphur in the mineralizing solutions forced the silver to deposit almost entirely in the native state, (7) absence of evidence that the arsenides functioned as silver precipitants, (8) lack of evidences of colloidal deposition.

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