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United States
Radcliff Mine

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 Location:
67 km NE from Ridgecrest, California, United States

  Regional Office:
Suite 605- 369 Terminal Avenue
Vancouver
British Columbia, Canada
V6A 4C4
Phone  ...  Subscription required
Fax604-692-0117
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  • Overview
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  • Mining
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Overview

StatusAbandoned
Mine TypeUnderground
Commodities
  • Gold
Processing
  • Leaching plant / circuit
  • Cyanide (reagent)
The Radcliff Mine recommenced preparation for operations in March 2014. The operator (Pruett Ballarat Inc.) of the mine constructed a new adit towards the high grade intercepts identified by drilling. The operator produced a bulk sample in the fourth quarter of 2016. A significant portion of this material – approximately 480 US tons – were delivered to the Midas mine / mill complex. On July 4, 2018, CMC Metals Ltd. announced that due to the low cutoff grade and low resource estimate expectation of the Radcliff Mine, the Company had relinquished its interest in the Radcliff Property and ended its joint venture.


Owners

Source: p. 1-3
CompanyInterestOwnership
Indirect
In April 2018, Bush Management Inc. acquired the property from Pruett Ballarat Inc. (PBI) through bankruptcy.

Deposit Type

  • Vein / narrow vein


Summary:

The World Beater property is underlain by a succession of metavolcanic and metasedimentary rocks where mineralization is found above a thickened metarhyolite formation (schistose gneiss of the World Beater Complex). The upper portion of the rhyolite is sericitized and silicified. The overlying submarine exhalite and tuff (chert and phyllite of the Radcliff Schist) and its accompanying massive sulfide mineralization and footwall mineralized hydrothermal alteration are characteristic of the volcanic-associated massive sulfide gold class of deposit (Poulsen and Hannington, 1995). More specifically, the deposit type is that in which gold is a primary commodity and base metals are of lesser economic importance. These deposits are gold deposits in a strict economic sense.

Gold mineralization found on the World Beater project to date is, for the most part, stratabound and primarily occurs within exhalative tuff units (phyllite and schist) of\ the Radcliff Schist. Thickness of the exhalative tuff may reflect paleotopography related to the primary topography of the rhyolite dome(s) (Comba, 1994).

The recognition of a distinct suite of bismuth and tellurium-bearing minerals (Schurer & Fuchs, 1993a) both in mineralized exhalite and in areas of mineralized hydrothermal alteration suggests that portions of the exhalite mineralization formed in proximity to underlying footwall structurally controlled mineralization (Marcoux et al., 1996; Poulsen and Hannington, 1995).

Gold mineralization at the World Beater property, specifically in the Radcliff mine area, can be found in several forms, with the present drill-indicated gold resource primarily in three stratigraphically separate and stratabound metasedimentary chert and sulfides horizons. The most significant of these horizons is a basal exhalite horizon that lies stratigraphically above the underlying World Beater Complex.

Gold mineralization is found in a mylonite shear zone at the base of the Radcliff Schist and was the focus of early mining activities (Long, 1993). This bedding-parallel shear is oxidized and fractured. At the Radcliff mine, seven levels, aggregating approximately 3,000ft (~1,000m) of tunnels and stopes over a vertical extent of 500ft (150m), were developed in this structural zone between 1898 and 1903. These workings produced approximately 15,000 ounces (~470kg Au) of gold from about 15,000 tons (~13,600 tonnes) of ore. In addition to the oxidized mineralization, siliceous and sulfidic gold-bearing exhalite has been encountered in these workings. The exhalite appears to be stratabound, contains pyrrhotite, and commonly has dark bluish-gray quartz. Limited studies on five samples of Radcliff area mineralization indicate that the gold occurs as micron-sized grains in a variety of mineral associations, both enclosed in, and adjacent to, grains of sulfides and/or gangue minerals. Gold also occurs as electrum. Bismuth is strongly associated with gold. Pyrite and pyrrhotite are the most common associated sulfide minerals (Schurer and Fuchs, 1993a).

In addition to the stratabound mineralization, gold occurs in quartz-sulfide veins, and as disseminated and locally massive sulfides emplaced along zones of shearing and dilatency within argillite and amphibolite that overlie quartzofeldspathic gneiss and granite of the World Beater Complex (CMC Metals Ltd. news release, December 21, 2011).


Mining Methods


Summary:

The Company’s business plan is to selectively mine “high grade” portions of an indicated resource at the Radcliff, with run-of-mine grade calibrated sub-sampling of mined material at the run-of-mine sub-sampling plant located at the 5510-level portal. Sampled material is submitted to an off-site laboratory.


Crushing and Grinding


Processing

  • Leaching plant / circuit
  • Cyanide (reagent)

Source: Subscription required

Summary:

CMC owns the Bishop mill facility, which has a current capacity of 50 tons per day; a proposed Plan of Operations under review by the BLM would increase the capacity to 100 tons per day. CMC intends to process ore from the World Beater property at the Bishop mill.

There have been five metallurgical “scoping studies,” there have only been a total of 24 wholeore leaching tests and a combined total of 10 flotation and gravity concentration tests. A comprehensive test program is now required to confirm the metallurgical response on a wider range of sample grades and mineralization types and to establish design criteria for a processing plant.

Metallurgical samples were derived from both core and RC cuttings. RC cuttings have undergone pulverization and, in some cases, put into slurry during sample transport from the bottom of the hole. Material changes to the samples may have occurred during these processes that could have affected metallurgical characteristics. It is ........



Reserves at January 9, 2015:

CategoryTonnage CommodityGradeContained Metal
Indicated 2,129,000 tons Gold 0.094 oz/ton 200,900 oz
Inferred 263,000 tons Gold 0.103 oz/ton 27,100 oz


Heavy Mobile Equipment:

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Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
Management Discussion & Analysis 2017
Technical Report 2015
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