Blacksand Beach Occurrence, Yakutat Mining District, Yakutat, Alaska, USAi

Regional Level Types
Blacksand Beach Occurrence	Occurrence
Yakutat Mining District	Mining District
Yakutat	City Borough
Alaska	State
USA	Country

The beach is in the Tongass National Forest.
Location: The Blacksand beach placer is about 10 miles long extending northwesterly between the Ahrnklin and Dangerous Rivers. The coordinate location is the approximate mid-point of the beach, which extends northwesterly into the Yakutat B-5 quadrangle. The deposit coincides with a named geographic feature (Blacksand Spit); it is location 7 of Cobb (1972). It is southeast of the Situk beach placer (YA007).
Geology: The Blacksand deposit is on a modern spit that extends along the coast line for about 10 miles. It was derived by high-energy reworking of underlying unconsolidated sediments of Holocene age (Foley and others, 1995; Reimnitz and Plafker, 1976) and from the density stratification of the alluvium constantly brought down by the Ahrnklin and Dangerous Rivers, which head in the Fairweather Range. Black and garnet sand lenses 0.1 to 0.2 feet thick contain interlocked magnetite-ilmenite or garnet and, more rarely, gold. Cobb (1979, p. 19) cites a reliable report of a PGE (platinum) from the mouth of the Situk River.
Workings: The beach has been mined on a small scale for many years. It was sampled by Thomas and Berryhill (1962), MacKevett and Plafker (1970; sample no. 67Apr76C), Reimnitz and Plafker (1976, samples 39, 40, and 41), and by Foley and others (1995, samples 276, 277 and 278). Thirteen beach locations were sampled by Thomas and Berryhill; their sample number 26 (table 12) contained 0.00012 ounce/cubic yard gold, 11.7 pounds/ cubic yard titania, and 25.8 pounds/cubic yard iron. Six of the thirteen samples contained 10 pounds or more of titania/cubic yard. The maximum amount of titania reported by Thomas and Berryhill was 47.4 pounds/cubic yard; maximum iron was about 150 pounds/cubic yard. Reimnitz and Plafker (1976) reported from 0.010 to 0.050 ppm gold in their samples. Gold was determined by atomic absorption, hence it may not correlate with the amount that could be recovered by placer mining and processing. Gold was not found by Foley and others (1995) in their head splits, but was reported in two of three spiral concentrates of the samples. Spiral concentrates also contained as much as 3.1 percent titanium and 1665 ppm zirconium.
Age: Holocene

Commodities (Major) - Au, Fe, Ti; (Minor) - PGE, Zr
Development Status: Yes; small
Deposit Model: Beach placer: single-cycle deposits of high-energy systems.

Other Databases

Link to USGS - Alaska:	YA008

Other Regions, Features and Areas containing this locality

References