The Monitor mine is located immediately south of Three Forks, British Columbia on the south side of Carpenter Creek.

The Slocan mining camp is dominated by fine grained to aphanitic clastic sedimentary rocks of the Triassic Slocan Group and consists of argillites, quartzites, limestones and some tuffaceous rocks. These sediments are frequently intruded by dikes, sills and stocks of varied composition and origin. Locally, southwest dipping slaty argillites with interbedded quartzite are intruded by quartz diorite and quartz porphyry dikes or sills.

The majority of the deposits are predominantly fault-fissure veins within distinctive zones and trends and replacement deposits where limestone or limy strata have been locally or extensively replaced by ore minerals. The Monitor lode occurs in a strong fault zone that cuts the sediments and displaces some dikes 2 metres. It has a general strike of 045 degrees, dips 60 degrees southeast to vertical and varies from a few centimetres to 1.2 metres in width. The widths have a tendency to decrease where it crosses a dike. The zone consists of brecciated hostrocks with lenses and veins of quartz, siderite and calcite mineralized with disseminated and massive galena, sphalerite and pyrite. The Monitor lode contains more gold on average than ore from any other lode in the area, producing 31,820 grams over 58 years. Some post-mineralization brecciation and shearing is evident.

Fault slickensides indicate an oblique normal-dextral movement to the northwest with later faults displacing the vein 7 to 20 metres which persists from surface to the lowest level of workings. The southwest extremity of the vein is terminated by a fault. Mineralization is more concentrated where the vein has been offset by later faults. Ore controls are not understood, however.

The Monitor lode is developed by five adit levels through a vertical range of 143 metres. The upper levels contained considerable oxidized mineralization with some lower levels containing increased pyrite content that carried high gold values. The best stoping area was above the No. 2 level, consisting of a nearly contiguous block 122 by 30 metres, stoped to surface. A second block at portal No. 3 was 61 metres long and a third, 40 metres long at the end of No. 3 level, was stoped up to the No. 2 level. The lode narrows at lower levels and the tenor of mineralization varies throughout its vertical extent.

Over its 56 year mine life, the Monitor mine produced 12,783,836 grams silver, 31,820 grams gold, 1,379,705 kilograms lead and 420,668 kilograms zinc from 18,308 tonnes ore.

The Min and Cork lodes are 580 and 730 metres southeast of the Monitor lode, respectively. They are short exploratory adits first driven in 1937.