Diamond placer occurrences are historically reported in Yukon and in the
adjacent areas of British Columbia and Alaska (Casselman and Harris,
2002) and are generally recovered during clean-ups on placer gold mining operations. While three stones from Crooked Creek in Alaska have been scientifically confirmed and described (Forbes et al., 1987), the same cannot be said of the Yukon diamond placer occurrences. In the Yukon, reports of a diamond discovery initiated sampling for diamond-indicator minerals that subsequently returned neither diamonds
nor their indicators (chrome-diopside, pyrope-garnet, picro-ilmenite). Furthermore, none of the known ultramafic rocks, diatremes of ultramafic-alkaline volcanic rocks nor high-pressure eclogites in Yukon and Alaska have been proven to be diamond-bearing. Alluvial diamonds are present along the West Coast in Oregon and California (Hausel,
1994) and exploration of diamond placers in California produced several hundred stones, including high-quality gems. However, all of these aforementioned occurrences lack diamond-indicator minerals common for cratonic diamond deposits, and no igneous diamond-bearing rocks are known in the area. Therefore, the placer occurrence of diamonds in Yukon as well the Pacific Coast remains enigmatic.
