No viable substitute for critical chromium
Stainless-steel ingredient mined in Alaska during both World Wars
Last updated 6/22/2020 at 11:05am
A vital ingredient in stainless steel and superalloys, chromium is considered by the United States Geological Survey as "one of the nation's most important strategic and critical materials."
"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, the only mineral of chromium metal, to help fill America's increased demand for chromium during both World Wars.
Alaska is second only to Montana when it comes to the best states to explore for future domestic needs of this important strategic and critical mineral.
No stainless substitute
Best known for being the primary ingredient of the smooth, mirrorlike 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 percent 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 buses and stripes down the center of American highways are lesser known yet highly recognizable uses of this element's pigment properties.
"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 percent 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.
"World stainless steel producers depend directly or indirectly on chromium supply," USGS wrote in its annual report, Mineral Commodity Summaries 2019.
Global chromium sources
While the U.S. consumes roughly 6 percent of the world's chromite ore production, none of this chromium mineral is mined domestically. Instead, America relies on foreign sources for approximately 71 percent of its supply of chromium, the balance comes from the domestic recycling of stainless steel.
Roughly 36 million tons of chromite was mined globally in 2018. Rich South Africa deposits accounted for around 44 percent of this production. The remaining 56 percent came from mines in Turkey (6.5 million tons); Kazakhstan (4.6 million tons); India (3.5 million tons); and other countries (4.5 million tons).
The U.S., which is not among the "other countries" that produced chromite, consumed roughly 550,000 tons of chromium, worth an estimated US$1.1 billion during 2018.
Domestic recycling supplied about 160,000 tons of this chromium. The balance was imported as chromite, refined chromium and chromium-containing scrap.
South Africa accounted for roughly 38 percent of the chromite and refined chromium metal imported into the United States last year. Kazakhstan (8 percent) and Russia (6 percent) were other suppliers of chromium.
The price of ferrochromium, the iron-chromium alloy used by the steel industry that is traded on global markets, is highly influenced by the health of the economy. As a result, the price of ferrochromium rocketed from around US60 cents per pound in 2006 to around US$2.80/lb in 2008 before plummeting again in 2009.
"The price of ferrochromium reached historically high levels in 2008 and then declined in 2009 with a weakening world economy. During the same time period, China's role as a chromium consumer has grown with its expanding stainless-steel industry," USGS penned in its chromium report.
Ferrochromium was down around US1.15/lb early in 2019.
Alaska's Chrome Queen
Looking around the United States for domestic sources of chromium, the USGS investigated both known types of chromite deposits – stratiform (layered) deposits such as the rich deposits mined in South Africa and podiform (pod shaped) deposits that developed in oceanic crust below the sea floor and have been pushed up by tectonic forces.
It is the podiform variety found around Red Mountain – situated near the southern end of the Kenai Peninsula in Southcentral Alaska – which provided the U.S. with a domestic supply of chromium during World Wars I and II.
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 40 to 42 percent chromium oxide.
Past investigations have identified 31 deposits at Red Mountain that contain at least 30 percent 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 percent 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.
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 percent chromium oxide ore remain at this area on the southern tip of the Kenai Peninsula.
Together, roughly 27,800 tons of ore averaging 42 percent 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.
Investigating 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. In fact, an investigation carried out by the U.S. Bureau of Mines in the early 1980s identified 94 podiform 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 and ones containing low-quality chromite, 41 hardrock deposits identified along Alaska's Border Ranges Fault during the BOM study are estimated to host 2.2 million tons of chromium oxide.
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 20.92 million cubic yards of placer material averaging 1.33 percent (556,000) tons 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."