Red Feather Claim
Larimer County, Colorado
Diamonds
PLACER, 60 acres
$15,000
History
The State Line kimberlite field is the largest known diamond district in the United States. Over 40 diamond-bearing kimberlites are known within an area of several hundred square kilometers, however most of the kimberlites are low grade. The major exception is the George Creek kimberlite dike system, which represents the highest-grade diamond deposit known in the United States!
The George Creek kimberlite dikes were discovered in 1983 by a team of Superior Oil and Lac Mineral geologists as a result of a stream sediment sampling program, followed by soil sampling, ground geophysics and exploratory trenching. On the first day of trenching with a backhoe in 1984, a diamond was found in a hand sample of kimberlite dike material, giving a glimpse of the high-grade nature of the kimberlite. Several 50-ton test pits were dug in the dikes that averaged about 75 carats per hundred tons (or “cpht”), well above the global diamond mine average grade of 35 cpht. Individual test pits contained up to 135 cpht, making the George Creek kimberlites by far the highest-grade primary diamond deposits yet discovered in North America. Based on these positive results, a further 3,300 tons were extracted, which yielded over 89,000 diamonds with a cumulative weight of 1,332 carats. A very high percentage of the stones (89-94%) were classified as colorless and the largest diamonds were up to 2 carats in weight.
Geology and Potential
The George Creek kimberlite dikes are deeply weathered and do not outcrop. The known kimberlite dikes proven through trenching are 8,500 feet long. However, it is possible that at least 17,000 feet of dikes exist in the headwaters of the creek based on previous geophysical surveys and geologic work.
Mining of the dikes themselves would be expensive and likely uneconomic due to their narrow widths. The placer diamond potential of diamonds eroded from the dikes downstream in George Creek is very high and has never been seriously investigated! The Red Feather Claims represent one of the few commercial diamond placer opportunities available in North America.
The Red Feather Claims are located 2 miles downstream of the dikes and encompass fully 0.8 miles along the bottom of George Creek. The claims were carefully selected for their favorable gradient and interpreted volume of gravel in this stretch of creek that should promote favorable placer development. In the upper part of the claim block the valley bottom is relatively narrow with a high stream gradient but swells to a large catchment basin 200 feet wide, all underlain by gravel with an accompanying 50% drop in stream gradient. This catchment basin should promote the accumulation of diamond-bearing placer gravels. The three contiguous claims are underlain by stream gravel over an area of 50,000+ square yards with likely depths to bedrock ranging from 1 to 5 yards.
Based on the grades of the George Creek dike system and their likely strike extent in the headwaters of the creek, as much as 50,000 carats of diamond would be eroded and washed into the creek for every ten meters of erosion the dikes experience. Considering regional incision rates since the Ice Ages, it is likely that 775,000 to 1 million carats of diamond have been liberated from the kimberlite dikes and concentrated into George Creek in the last few million years.
A few mini-bulk samples of gravel dug from test holes where the gravel is shallow in the western part of the property were run through a sluice box during testing of the property, yielding five typical George Creek diamonds with high transparency and white color. This is a highly encouraging result and further tests are needed to evaluate the commercial potential of these diamond placers! Bedrock was not reached in any of these test holes and careful prospecting may disclose trap sites with very high diamond concentrations.
Diamonds photos in the gallery below are of diamonds recovered from the dikes by Superior Oil.
