Mining Intelligence and News
United States

Moonlight-Superior Project

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Mine TypeOpen Pit
StagePreliminary Economic Assessment
  • Copper
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Mine Life... Lock
SnapshotObjectives for 2023:
- Moonlight deposit: Drill and define oxide resource.
- Superior deposit: Define a high-grade pit and establish gold and silver credits.
- Update PEA by adding starter pits with gold/silver credits and Moonlight oxide.


US Copper Corp. 100 % Indirect
Effective June 28, 2013, the US Copper Corp. (formerly Crown Mining Corp.) purchased a 100% interest in the Superior Project, subject to an underlying production royalty, which included 132 unpatented mining claims and a lease on 36 patented claims in Plumas County, California for $50,000.

On February 26, 2016, the US Copper Corp. entered into an agreement with Canyon Copper Corp (“Canyon”) to acquire a 100% interest in the Moonlight Property (the “Agreement”), subject to an underlying production royalty. Under the terms of the Agreement US Copper acquired a 100% interest in the Moonlight Property for consideration of $375,000 and 2,750,000 common shares of the Company.

Deposit type

  • Breccia pipe / Stockwork
  • Porphyry
  • IOCG


The Moonlight deposit was historically classified as a porphyry copper deposit with associated gold, silver, and molybdenum credits. However, Placer-Amex geologists recognized that the Lights Creek Distric (LCD) deposits had many characteristics that were not typical of porphyry copper deposits and lacked many of the typical features. L.O. Storey (1978) noted, “Typical porphyry copper type alteration zonation as illustrated by Lowell and Guilbert is nonexistent.” Recent work noting the lack of porphyry style veining, the ubiquitous presence of magnetite at Superior and specular hematite at Moonlight, and the relative scarcity of pyrite suggest an IOCG affinity (Stephens 2011) (Cole 2015).

Regarding IOCG deposits, Sillitoe (2003) noted, “The deposits…reveal evidence of an upward and outward zonation from magnetite-actinolite-apatite to specularite-chloritesericite and possess a Cu-Au-Co-Ni-As-Mo-LREE (light rare earth element) signature…”. The high-grade mineralization at Superior is associated with magnetite-actinolite-tourmaline-apatite. At Moonlight, copper mineralization is associated with tourmaline-specularite-chlorite-sericite. During an April 2015 field visit to the district Sillitoe categorized Engels, Lambs Ridge, Superior and Moonlight as IOCG deposits (Cole 2015).

According to Placer-Amex surface maps, several intrusive phases host the Moonlight deposit. A large part of the deposit lies within two phases of the LSC quartz monzonite designated as QM III and QM IV. Granitic intrusive (Gr V) hosts the southern third of the deposit. Granodiorite carries copper mineralization at the northern tip of the deposit. Jurassic-Triassic roof pendant meta-volcanic rocks overlay the deposit and crop out on the southern, western and northern perimeters. On the western flank of the deposit meta-volcanic rocks are overlain by Tertiary sediments.

Multiple intrusions at Moonlight were not logged in the Sheffield drilling and were not confirmed by QPs preparing the report. Some of the variations in intrusion texture and composition may be related to hydrothermal alteration.

The bulk of the following discussion is after R. G. Wetzel from his January, 2009 report describing the Moonlight deposit. Placer-Amex, Sheffield, and Sheffield's successors recognized that there are at least two styles or stages of mineralization at the Moonlight deposit. The paragenetically earlier style is characterized by disseminated copper minerals located interstitial to quartz, feldspar, chlorite and especially disseminated rosettes of tourmaline. This mineralization usually consists of fine-grained chalcopyrite but zones of disseminated bornite are also common. High in the system disseminated hypogene chalcocite has also been occasionally observed. Bornite rims chalcopyrite grains in some places. This style of mineralization shows some association with potassium feldspar, a very strong association with tourmaline and sometimes chlorite. Unless overprinted by second stage fracture or breccia hosted mineralization, this earlier style of mineralization typically assays at 0.1% to 0.8% copper. The second stage of mineralization is characterized by veinlets, or stockwork breccias, which often have a gangue of tourmaline and lesser quartz with strong hematite. Strong copper mineralization is commonly observed on veinlets trending N20-35W and dipping 15- 35SW southwest. The vein orientation suggests a good exploration target beneath the meta-volcanic rocks to the southwest. In addition to the mineralization in shallow dipping fractures, copper is contained on north-south, steep to moderately east dipping veinlets, N60-75E steeply north dipping veinlets, and N70-85W steeply south dipping veinlets. Although fracture hosted mineralization is widespread and often high grade at Moonlight, drilling to date has not revealed extensive vein-like structures similar to those mined at the Superior Mine.

The copper sulfides show a vertical zonation, with chalcocite or digenite predominating in the upper levels of the deposit. With increasing depth, bornite predominates and chalcopyrite appears. Bornite is often observed to rim or cut chalcopyrite. Bornite and chalcopyrite may also be cut by chalcocite veinlets. At the deeper levels chalcopyrite typically dominates in fracture hosted mineralization, but bornite is often still abundant. Magnetite can sometimes appear with hematite decreasing in abundance with depth. Rare pyrite may appear in veinlets at depth. Iron or magnesium-rich carbonates are also common in fracture hosted mineralization. Late-stage copper-poor calcite and quartz veinlets that cut both preceding types of mineralization are also common.

Veinlet-or-breccia hosted mineralization dominates the northern part of the Moonlight deposit, where chalcocite-rich mineralization commonly grades more than 1% copper. In holes 06MN-9, 10, 11, and 12 chalcocite-rich mineralization grades quickly into chalcopyrite with depth and bornite is not very abundant. In the southern and central parts of the deposit the chalcocite-bornite-chalcopyrite zonation is well-developed. Fracture-hosted mineralization may grade more than 1% copper in the central and southern portions of the deposit.

Sericitic, chloritic, and albitic alteration may form halos around veinlets and breccia zones. Epidote becomes more abundant in and around veinlets with depth. Potassium feldspar is abundant. In addition to the quartz, feldspar and 1 to 5% disseminated tourmaline that characterizes the Lights Creek quartz monzonite, it also contains 2 to 8% finely disseminated hematite and magnetite. The hematite is typically specular and thin section work indicates that it usually rims and replaces magnetite. Hematite replacement decreases with depth with the result that the LCS at Moonlight becomes increasingly magnetic with depth.



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CommodityProductUnitsAvg. AnnualLOM
Copper Concentrate kt 1482,507
Copper Payable metal M lbs 1,492
Copper Metal in concentrate M lbs 1,547
Silver Payable metal koz 16,635
Silver Metal in concentrate koz 19,141

Operational metrics

Daily processing capacity 60,000 tons *
Annual processing rate 21,469 k tons *
Annual processing capacity 21,896,000 tons *
Stripping / waste ratio 0.78 *
Waste tonnes, LOM 285,879 k tons *
Ore tonnes mined, LOM 364,967 k tons *
Total tonnes mined, LOM 650,846 k tons *
Tonnes processed, LOM 364,967 k tons *
* According to 2018 study.

Production Costs

Assumed price Copper USD 3.15 / lb *  
Assumed price Silver USD 18 / lb *  
* According to 2018 study / presentation.

Operating Costs

OP mining costs ($/t mined) USD 1.2 *  
OP mining costs ($/t milled) USD  ....  Subscribe
Processing costs ($/t milled) USD  ....  Subscribe
G&A ($/t milled) USD  ....  Subscribe
Total operating costs ($/t milled) USD  ....  Subscribe
* According to 2018 study.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M USD  ......  Subscribe
Equipment leasing costs $M USD  ......  Subscribe
Sustaining CapEx $M USD  ......  Subscribe
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OP OpEx $M USD  ......  Subscribe
Processing OpEx $M USD 1,740
G&A costs $M USD 237
Total OpEx $M USD  ......  Subscribe
Total Taxes $M USD  ......  Subscribe
Gross revenue (LOM) $M USD  ......  Subscribe
Net revenue (LOM) $M USD  ......  Subscribe
Net Operating Income (LOM) $M USD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax Cash Flow (LOM) $M USD  ......  Subscribe
Pre-tax NPV @ 8% $M USD  ......  Subscribe
After-tax NPV @ 8% $M USD  ......  Subscribe
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Mine Management

Job TitleNamePhoneRef. Date
....................... Subscription required ....................... Subscription required ........... Subscription required Feb 2, 2023

Total WorkforceYear
...... Subscription required 2018


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