The Marilyn 1-12 occurrence is located about 5 kilometres southeast of Ymir, 1.0 kilometre north of Porcupine Creek. An old adit and several open cuts are present on the property.

The area lies along the faulted contact between Lower Cambrian sediments (possibly correlative with the Hamill Group) and what is believed to be limestones and dolomites of the Ordovician Active Formation.

The mineralized showings lie south-southwest of the Oxide showing (082FSW022). Mineralization occurs along a limestone-dolomite contact near faulted contact with white quartzite. Within the mineralized zone is a 30.5 metre long quartz vein which is traceable for approximately 60 metres. Disseminated galena is present in a quartz vein within the old workings.

In 1980, a sample from the old adit assayed 173.48 grams per tonne silver and 1.68 per cent lead. Another sample taken along the limestone-dolomite contact assayed 447.76 grams per tonne silver, 6.65 per cent lead and 0.3 per cent zinc (Assessment Report 9094). Samples from an old dump assayed 246.85 grams per tonne silver and 7.6 per cent lead (Assessment Report 9094).