Barite co-product may add value to Palmer

Constantine Metal Resources Ltd. Aug. 13 reported that results from metallurgical testing demonstrate a premium-quality barite concentrate can be produced as a co-product to the copper, zinc, gold and silver found in the volcanogenic massive sulfide deposit at the Palmer project in Southeast Alaska.

According to a resource calculated in 2015, the South Wall-RW deposit at Palmer hosts 8.1 million metric tons of inferred resource averaging 5.25 percent (940.4 million pounds) zinc, 1.41 percent (252.6 million lb) copper, 0.32 g/t (83,600 ounces) gold and 31.7 g/t (8.3 million oz) silver.

This resource area is made up of 13 to 15 percent barium, which equates to roughly 22 to 25 percent barite by weight.

This year's metallurgical work was designed to quantify the recovery of barite, a mineral that would otherwise become waste generated in the production of copper and zinc concentrates.

This work demonstrates that 91.1 percent of the barite at Palmer can be recovered in a clean high-grade concentrate with a specific gravity of 4.44.

The specific gravity is important for barite's primary use, as a weighting agent in drilling mud for oil and gas exploration and development. American Petroleum Institute prefers a 4.2 specific gravity for barite used in oil and gas drilling but has lowered this minimum specific gravity requirement for barite to 4.1 in 2010.

In addition to a specific gravity well above requirements, Constantine reports that the testing shows that a barite concentrate from Palmer meets all American Petroleum Institute and U.S. Environmental Protection Agency specifications for oilfield drilling grade barite, including particle size and purity, and appears to be a market-ready product.

"These results confirm that a premium-quality barite concentrate can be produced from the copper-zinc ores at Palmer, and that it can be achieved by the addition of simple steps to mineral processing," said Constantine Metal Resources President and CEO Garfield MacVeigh. "This may have very positive implications with the potential to both enrich gross metal value per tonne (metric ton) and provide significant environmental and operational benefits by reducing waste."

With the metallurgical results showing quality barite can be recovered from Palmer, a market study by experts in the industry has been commissioned to assess wholesale barite price for different North American oil basin markets.

Preliminary estimates range from US$170 per short ton to US$225 per short ton.

The study will also include an analysis of transportation options and cost to access the most likely of these markets. Alaska, with its oil and gas fields on the North Slope and in Cook Inlet, would be a good market for Palmer barite.

While the U.S. Geological Survey withholds information on domestic barite production, it is estimated that more than 75 percent of the roughly 3 million metric tons of barite used in the United States each year is imported, with China being the largest supplier of this weighting agent.

Due to this reliance on overseas sources for a material vital to America's oil and gas sector, USGS has listed barite on its 2018 list of 35 minerals critical to the United States.

Being within 40 road miles of the Pacific Rim deep-water port at Haines, Palmer is expected to have a significant competitive advantage to delivering barite in North America. Adding to this advantage is that the barite would be a co-product of copper and zinc production that is otherwise already being mined and milled.

In addition to the promising barite results, the metallurgical work also confirms and enhances the attractive mineral processing characteristics for the copper and zinc concentrates produced by previous testing. This includes a significant improvement in zinc recoveries to 93.1 percent to a concentrate grading 61.3 percent zinc; an 8.2 percent improvement in recovery, as well as an increase in zinc concentrate grade, over previous tests.

This year's metallurgical work also reproduced the high copper recoveries of 88.9 percent to a concentrate grading 24.5 percent copper identified in previous testing.

Combined silver and gold recovery to copper and zinc concentrates of 90.6 and 69.6 percent, respectively, with the large majority of the precious metals reporting to the copper concentrate.

"The 93 percent zinc recovery with 61 percent zinc concentrate grade are also very important value-added results," said MacVeigh. "By all metrics, Palmer demonstrates excellent metallurgical qualities with high recoveries for all key commodities to desirable high-grade concentrates."

The Palmer project is being advanced by a joint venture between Constantine (51 percent) and Dowa Metals & Mining Co. Ltd. (49 percent).

In addition to the metallurgical work, the roughly US$9 million exploration program budgeted by the partners for 2018 includes approximately 10,000 meters of drilling to expand the South Wall-RW resource as well as explore targets across the wider property.

Over the three years since a resource was last calculated for Palmer, drilling has tapped new areas of copper- and zinc-rich mineralization at South Wall. This drilling, along with the 2018 program, will be incorporated into a new resource calculation slated for later this year.

This updated resource, along with the new metallurgical understanding, will form the basis of a preliminary economic assessment for Palmer, the first ever look at the viability of developing a mine at the VMS project.

–SHANE LASLEY