Seminoe Mountains, Carbon County, Wyoming, USA.

The gravel on the claim is very coarse and boulders up to 3 feet in diameter are common. The modal clast size is very coarse at around 5 inches. The gravels contain sparse amounts of clay and are poorly indurated. This combination makes the gravels easy to wash. The gravels nearest the surface are loosely cemented by caliche, as is typical in most arid soils, but it does not interfere with gold recovery at deeper levels. Black sand is abundant, particularly in pay streaks, but the majority is magnetic, making separation from the fine placer gold easily achievable. The gravel clast population is dominated by various granitic rocks exposed in the core of the Seminoe Mountains uplift to the south. These clasts are usually fresh and unweathered, making their separation from the finer, gold-bearing fraction easy. The gravels also contain abundant clasts of dark colored banded iron formation derived from the western end of the Seminoe Mountains in the Seminoe Greenstone Belt. These heavy cobbles provide visual guidance to richer portions of the gravel sequences. As field tested in the trench exposures, lenses of gravel with a higher accumulation of coarse banded iron pebbles and cobbles yield more abundant flake gold.

Bedrock seen in trench exposures consists of soft tuffaceous sandstones of the Miocene-aged Split Rock Formation. Samples panned exclusively from Split Rock exposures have also yielded abundant black sand and fine gold that represents a separate resource on the claim. The soft Split Rock Formation was an easily erodible surface for the powerful North Platte River and the bedrock contact is marked by numerous, irregular scours. Several of these have been tested through selected sampling by Tenmile Resources and have yielded some exceptional placer grades.
A few carefully controlled test samples were processed to obtain accurate placer grades on the Diamondback claim. 3 cubic yards of material collected from the entire vertical sequence of gravels yielded a grade of 0.12 ounces of gold per cubic yard. Individual 1-gallon samples taken at favorable locations, such as scours in bedrock have yielded higher grades, though these are localized. Churn drilling or trenching is needed across the entire property to determine commercial potential but preliminary results are encouraging. For a moderate-sized placer deposit, the placer grade at Diamondback is very high. Samples taken at regular intervals across the entire 20 acres have all yielded gold at grassroots level. Preliminary mapping of paystreaks has been conducted across the surface of the claim through population density of banded iron cobbles. A few of the new identified paystreaks have been sampled and yielded coarse flakes. It is the opinion of Tenmile Resources that this claim represents an excellent hobbyist claim or common club claim for a larger group. Commercial exploitation of the gravels may be achieved utilizing a recirculating water system. The flat terrace provides unlimited disposal ground for tailings.

The placer gold displays a near universal morphology of flat, thin flakes indicative of significant transport distances. This would tend to support the interpretation that the vast majority of the coarse flake gold was derived from reworked terrace gravels of Hurt Creek draining southeast from the Seminoe Greenstone Belt. Though not large, the gold flakes are abundant. Some recovered flakes are larger than 1/10 inch across. In addition to the flakes, there is an abundant amount of very fine flour gold derived from the underlying Split Rock Formation or potentially from a large disseminated lode gold deposit discovered in the Archean-aged Kortes Dam Granite to the south by Tenmile Resources. Some of this fine gold is subangular and could not have come the 20 miles or so required for the larger flakes.

As indicated by careful testing, the placer claim contains an economic quantity of gold. A rough resource estimate based on field observations and detailed sampling indicates a probable gravel resource of 113,000 cubic yards of gravel on the claim to a depth of 5 feet containing an estimated 13,560 ounces of placer gold.

The gravels contain other resources of interest to rockhounds and amateur gold enthusiasts. Some of the banded iron cobbles are beautiful lapidary-grade material containing alternating bands of red jasper, hematite, and silicified grunerite commonly called “tiger iron”. Some of the silicified grunerite bands are a beautiful form of “tiger’s eye” that would yield attractive specimens. Several lode nephrite jade occurrences are known in the immediate vicinity of the Diamondback placer and a few small pebbles less than 1 cm diameter of deep green nephrite jade have been found through a cursory inspection of the gravels. Larger cobbles and boulders of green to black nephrite jade have been recovered from pediment surfaces on both sides of the Seminoe Mountains. Thus, larger pieces of water worn nephrite are not out of the question in the claim gravels.

Photo Descriptions:
View from claim to N Platte river and Seminoe Mountains View of 10-12 ft of grvel in the old gravel exploratory trench on the Diamondback claim Excellent road access along length of claim Course (>35 mesh) gold flakes from test samples of Diamondback claim gravel Closeup view of gravels in trench