Mineral Facts and Problems: 1960 Edition Page: 393

                                
INDIUM
By Donald E. Eilertsen I
HE INTRODUCTION of transistors heralded a new electronic age, and
a new important use for indium was born. Older uses for indium are in
sleeve bearings and in low-melting alloys.
SUMMARY

In 1924, 61 years after indium's discovery,
the world supply of the metal could have been
held in a teaspoon. Then a silverware firm in
the United States became interested in the
metal for making nontarnishable silverware
and began searching for indium. It was first
found and extracted from Arizona sphalerite,
but later a larger supply was found in Montana
zinc-plant flue dusts.
Indium has been identified in about 50 min-
erals, yet no mineral contains the element con-
sistently. Sphalerite is the commercial source
of the metal. When zinc and zinc-lead ores are
processed, indium, if present, remains in various
residues, dusts, or in crude zinc and lead, and
after many steps in refining, the metal is re-
covered for commercial use.
Two firms in the United States and one firm
each in Canada and South America produce
most of the world supply of indium. The
United States is the largest indium consumer,

and in 1957, the peak year, markets were found
for almost 20 tons of domestic and imported
indium. The U.S. resource of indium, obtain-
able as a byproduct in zinc production, is
roughly estimated at 320 short tons.
Indium is used principally in electronic de-
vices, in sleeve bearings, and in special alloys
for dental casts, fusible safety plugs and links,
and solders.
In 1958 the small quantity price of 99.9 per-
cent pure indium was $2.25 a troy ounce, and
quantities of 5,000 or more troy ounces brought
$1.25 to $2.25 a troy ounce. 99.999 percent in-
dium was available at higher prices.
Research on indium in recent years has been
centered on the properties of the element and
its compounds for specialized uses in the elec-
tronics field.
The outlook for indium is continued growth
of the industry and greater demand for the
element.

BACKGROUND

Indium was discovered in 1863 by Professor
Ferdinand Reich and his assistant Theodor
Richter in Freiburg, Germany, when spectro-
graphic studies for thallium on a sample of
sphalerite revealed some undiscovered indigo-
blue lines. The newly discovered element was
named indium from the characteristic lines of
its spectrum, and late that year the metal was
isolated.
A teaspoon could have held the world stock
of indium in 1924 when Oneida Community,
Ltd., Oneida, N.Y., became interested in indium
to make nontarnishable silverware (6).2  In
1926 William S. Murray, now President of the
Indium Corp. of America, Utica, N.Y., led a
search and found indium at an abandoned pros-
pect, the Beebe property near Kingman, Ariz.
About a thousand tons of ore was mined, and
I Commodity specialist.
SItalicized numbers in parentheses refer to items in the
bibliography at end of chapter.

250 ounces of indium was produced. In 1929
a dependable source of indium raw material
was found in the Cottrell dusts from smelting
Montana zinc ores, and a process for electro-
plating indium was developed. In 1934 an
indium alloy for dentistry was made, and this
was the first commercial use for the element.
SIZE AND ORGANIZATION OF THE INDUSTRY
The American Smelting & Refining Co.,
Perth Amboy, N.J., and the Anaconda Co.,
Great Falls, Mont., are the only firms in the
United States that are producing indium, and
both companies have produced it since about
1940.  Other firms discontinued production
because the demand was small, and indium was
too costly to recover.
The Consolidated Mining & Smelting Co. of
Canada, Ltd., Trail, British Columbia, has
produced indium since 1941, and Cerro de
Pasco Corp., La Oroya, Peru, since about 1945.
393