Irreplaceable chromium deposits in Alaska
Border Ranges offers 600 miles of chromite hunting grounds Critical Minerals Alaska 2020 – Published October 29, 2020
Last updated 12/23/2020 at 4:33am
While the United States consumes roughly 5% of the chromite mined globally, none of this chromium mineral comes from domestic mines. Instead, America relies on foreign sources for approximately 72% of its supply and the balance of this vital ingredient in stainless steel and many superalloys comes from recycling.
Nearly all America's chromite imports come from one country, South Africa.
This heavy reliance on one country, coupled with a dearth of alternatives for this vital stainless-steel ingredient, lands this chromium mineral on the U.S. Geological survey's list of minerals critical to the U.S.
"Because there is no viable substitute for chromium in the production of stainless steel and because the United States has small chromium resources, there has been concern about domestic supply during every national military emergency since World War I," the USGS explains.
Rich chromite deposits on Alaska's Kenai Peninsula were able to ease some of these concerns by providing a domestic supply of chromite to help fill America's increased demand for chromium during both World Wars.
No stainless substitute
Best known for being the primary ingredient of the smooth, mirrorlike chrome plating on automobiles, chromium is a highly prized alloy due to the hardness and corrosion resistance it lends to other metals.
By far the largest use of chromium is in stainless steels, which typically contain 10.5 to 32% of this critical alloying metal.
This strategic metal also lends its hardness and corrosion-resistant properties to superalloys, specialty metals that can maintain their integrity in extreme conditions.
"Chromium in superalloys (high-performance alloys) permits jet engines to operate in a high-temperature, high-stress, chemically oxidizing environment," USGS inked in an informational page on the metal.
The properties chromium imbues into alloys, coupled with limited domestic supply, is why the geological survey considers it a critical and strategic metal.
While shiny bumpers, hubcaps and tailpipes are obvious applications of chromium's properties, yellow school busses and stripes down the center of American highways are lesser known yet highly recognizable uses of this element's chromatic traits.
"School bus yellow, originally called chrome yellow for the chromium pigment, was adopted for use on school buses in North America in 1939 because black lettering on the yellow buses is easy to see in the semidarkness of early morning," the USGS explained.
In fact, chromium derives its name from the Greek word for color, chroma, due to the intense coloration of many chromium compounds.
Interestingly, chromium impurities give some of our most prized gems their brilliant colors. The colorless corundum crystal is a ruby with the addition of chromium, and a bit of chromium changes the geometry of the atoms of beryl slightly, resulting in emeralds.
While chromium derived its name from its pigmentation qualities, it is the durability this metal lends to alloys that drives its demand.
Roughly 85% of the world's chromium is used for stainless steel and chrome plating, and the metal has no equal when it comes to the anti-corrosive and hardness qualities.
"Chromium has no substitute in stainless steel, the leading end use, or in superalloys, the major strategic end use," USGS wrote in its annual report, Mineral Commodity Summaries 2020.
Global chromium sources
Roughly 44 million tons of chromite was mined globally during 2019. South Africa and Katakhstan, the epicenter of global chromite ore, accounted for roughly 54% of this production. The balance was mined primarily in Turkey, India, and Finland.
"South Africa was the leading chromite ore producer," USGS penned in its 2020 Mineral Commodities Summaries. "Increased labor costs, increased costs for electricity, an unreliable supply of electricity, and challenges related to deep level mining, together with the decreasing cost of chromite ore, could affect production in South Africa."
This could be a problem for the U.S., which received 99% of the roughly 370,000 metric tons of chromite imported during 2019 from South Africa.
The U.S. also imports chromium metal and chromium containing scrap.
South Africa accounted for roughly 38% of the combined chromite and refined chromium metal imported into the U.S. last year. Kazakhstan (8%) and Russia (6%) where other significant chromium and chromite sources.
Alaska's Chrome Queen
Red Mountain, located near the southern tip of Alaska's Kenai Peninsula, has previously supplied America's wartime chromite needs and still holds stores of the critical mineral.
Chromium-rich mineralization was discovered in the Red Mountain area around 1910 and some limited mining occurred there during World War I.
Knowing Red Mountain could provide a domestic source of chromium during World War II, the U.S. Bureau of Mines drilled more than thirty holes to evaluate this chromite-rich area near the Southcentral Alaska town of Seldovia. This exploration resulted in development and mining at Chrome Queen and other orebodies discovered over a four-mile-long area at Red Mountain.
From 1942 through 1944, production from the Chrome Queen mine totaled 6,650 tons of ore averaging 40 to 42% chromium oxide.
Past investigations have identified 31 deposits at Red Mountain that contain at least 30% chromite and 20 of these are estimated to contain roughly 97,000 tons of chromium oxide. Three other lower grade deposits in the area are estimated to host another 1.5 million tons of chromium oxide.
No resource was calculated for the 11 other high-grade deposits due to small size or lack of exposure.
In total, about 26,000 tons of ore containing 38 to 43% chromium oxide was produced from Red Mountain from 1942 to 1958, and about 1.6 million tons of ore is estimated to remain in deposits historically investigated there.
In addition to hardrock deposits, the Bureau of Mines identified a rich chromium placer deposit in the Windy River valley, which drains Red Mountain. Sampling of this deposit by Anaconda Minerals and BOM outlined 20.9 million cubic yards of placer material averaging 1.33% (556,000 tons) chromium oxide.
Additional chromium was identified at Claim Point, an area about 15 miles southwest of Red Mountain that underlies Chrome Bay and extends for about 1,000 feet onshore.
Roughly 2,000 tons of ore was mined from the tidewater deposits at Claim Point and results of drilling and surface sampling indicate 295,000 tons of 17.8% chromium oxide ore remain at this area on the southern tip of the Kenai Peninsula.
Together, roughly 27,800 tons of ore averaging 42% chromium oxide, having a chromium-to-iron ratio of 2.75-to-1 was mined from the chromite deposits at Red Mountain and Claim Point.
Much of the chromite deposits at the southern tip of the Kenai Peninsula are on lands owned by Cook Inlet Region Inc., more commonly known as CIRI, an Alaska Native Claims Settlement Act (ANCSA) regional corporation.
Exploring the Border Ranges
While Red Mountain and Claim Point are the best-known chromite deposit areas in Alaska, they are far from the only ones found here. An investigation carried out by the U.S. Bureau of Mines in the early 1980s identified 94 chromite deposits along a 600-mile stretch of the Border Ranges Fault that arcs 600 miles southwest from McCarthy to the southwestern tip of Kodiak Island.
While most of these were considered sub-economic at the time, the number of prospects indicate Alaska's potential as a future source of this critical and irreplaceable mineral.
Excluding all deposits more than 10 miles from tidewater or existing roads, as well as those containing low-quality chromite, 41 hardrock deposits identified along Alaska's Border Ranges Fault are estimated to host at least 2.2 million tons of chromium oxide.
Three of the hardrock chromite prospects along the Border Ranges Fault are found at Tonsina, an area east of the Richardson Highway at about milepost 80.
Two of these – Bernard Mountain and Sheep Hill – are found on the Genesis property recently picked up by New Age Metals Inc. The third – Dust Mountain – is on lands owned by Ahtna Corp., an Alaska Native corporation.
While New Age Metals is primarily interested in the platinum group metals also found on Genesis, the two main complexes there are known to host chromite.
Historical investigations have located 15 chromite deposits and occurrences at Bernard Mountain. Bureau of Mines estimates that three of the surfacing deposits there contain 343,000 tons of chromium oxide. Sampling indicates that the Bernard Mountain chromite can be concentrated to meet the metallurgical-grade specifications for the alloying metal.
Another 12 chromite deposits and occurrences were identified on Sheep Hill and Dust Mountain.
One deposit at Sheep Hill is estimated to contain 26,000 tons of chromium oxide. Not all the chromite found in this deposit, or the other occurrences on Sheep Hill and Dust Mountain, however, is considered able to be concentrated to the specifications needed for alloying.
Numerous other occurrences have also been identified in the Chugach Mountains from near the Sheep Mount Lodge on the Glenn Highway to the Eklutna area near the town of Palmer.
From Eklutna, the Border Ranges Fault runs south on the Kenai Peninsula, through the Red Mountain and Claim Point area and onward to the adjacent Afognak and Kodiak Islands, where five other chromite-bearing mafic or ultra-mafic complexes have been identified.
Hints of chromite
In addition to the chromite deposits found along the Border Ranges Fault, numerous occurrences of the critical alloying metal have been identified across Alaska. Small and scattered, however, these prospects have not resulted in a find considered to be an important source of chromite.
These hints of chromite, however, might add up to something in the future.
"Mineral resource assessments are dynamic. Because they provide a snapshot that reflects our best understanding of how and where resources are located, the assessments must be updated periodically as better data and concepts are developed," USGS penned in its chromium facts sheet. "Current research by the USGS involves updating mineral deposit models and mineral environmental models for chromium and other important nonfuel commodities and improving the techniques used to assess for concealed mineral resource potential."