Prospecting for Barite
Circular No. 4, February, 1981, revised 2001
by Ken A. Phillips, Mineral Resource Engineer &
Clifford J. Hicks, Field Engineer
The mineral barite, barium sulfate, BaSO4, is unusually heavy with
a specific gravity of 4.2 - 4.6. This means it is that many times
as heavy as an equal volume of water and that it is over half again
as heavy as most common rocks such as granite, lava, sandstone, and
limestone. This heft is most noticeable in a fist-sized specimen. The
mineral is moderately soft. A fingernail cannot scratch it, a copper
penny may or may not, but a knife blade will.
A few other minerals may be mistakenly identified as barite:
Witherite (another barium mineral), celestite and strontianite (both
strontium minerals), cerussite and anglesite (both lead minerals)
and hydrozincite (a zinc mineral) also have a high specific gravity,
similar color (colorless, white, yellow, gray, green, blue and red) and
a nonmetallic appearance. They are rare and also of potentially greater
value than barite. In fact, the identity of any heavy mineral should be
determined. No prospector should ignore any other potentially valuable
mineral de-posit by searching only for barite.
A specific chemical test for the element barium is given in Field Tests
for The Common Mineral Elements, Arizona Bureau of Geology and Mineral
Technology, Bulletin 175, by George H. Roseveare. The test is not simple
or specific for barite, as it will indicate the presence of barium in
any mineral or rock. A note of caution, barium typically occurs as a
constituent of light colored igneous rocks at a concentration of 0.07%
to 0.50%. The semi quantitative spectrographic analysis often purchased by
prospectors will nearly always show a concentration of 0.50% barium. This
may be expected, has little significance to the barite prospector,
nor does such a low value have any economic significance.
There are two tests for barite that are simple and usually specific,
though not always:
- The first test requires an ultra-violet (mineral) light and an
alcohol lamp with a blow pipe or a propane torch. Frederick
H. Pough de-scribes the test in his A Field Guide To Rocks and
Minerals. "Barite is only occasionally fluorescent, but all
barite samples tested were found to be fluorescent yellow orange
after roasting. Hence, with two similar minerals (celestite and
barite) we have only to roast an edge intensely in the flame
(to red heat, briefly), allow them to cool, and examine them
with our ultraviolet light. The orange one will be barite,
the yellow green one, celestite."
- The second method requires only a steel prospector's pick. When
a barite sample is scratched across the head of the pick it
adheres to the steel leaving a distinctive white streak. Other
white rocks usually leave only a scratch or nothing.
Field prospecting for barite, like any other mineral, should be
preceded by a study of typical types of occurrences and areas of past
discoveries. Commonly white to gray, barite occurs in veins, replacements
or residual deposits commonly associated with quartz, fluorspar and
calcite. Deposits may be sought in highly weathered (rather crumbly or
fractured) rocks especially those of Cambrian or Ordovician age, which
overlay carbonate rich rocks such as limestone. Nearly all the barite
deposits in Arizona, however, occur in veins associated with faults,
breccias and fracture zones. Most of these are in igneous rocks, some are
in sedimentary and a few are in metamorphic rocks. The veins are typically
a few feet wide and usually have been traced for only a few hundred feet
in outcrop. Even less is known about the extent of the veins at depth.
The geochemistry of barium in the earth's surface environment is complex
and not fully understood. Under some conditions, barium is released
from weathered igneous rocks, carried to the sea and precipitated
as barite. Some deposits in sedimentary rocks may form in this
manner. Prospecting for this type of barite occurrence first requires
a determination of the location of marine sediments. The regional
delineation of barite beds may be best determined by panning. Most
extensive areas of sedimentary rocks contain very limited heavy
minerals. Check any panned "heavies" with the ultraviolet light.
Barite's specific gravity is only 13% lower than the mineral magnetite,
which is the magnetic constituent of the placer miners familiar
"black sand." Fragments of barite in a stream, wash or
crushed outcrop will concentrate with the black sand in a pan. Unlike
gold, however, barite will not travel far from its outcrop before it
is crushed to slime size particles by tumbling action. The other heavy
minerals mentioned previously (witherite, celestite, cerussite, anglesite,
hydrozincite) can also be concentrated by panning. Any barite found in
the pan should then be traced upstream until an outcropping or residual
hillside source is found. However, as barite is a common gangue mineral in
vein deposits, many occurrences found in this manner will be too low grade
or too small. The barite must occur in such a mode as to either be of
a minimum specific gravity of 4.25 or is amenable to simple concentration.
Principal uses for barite are as a weighting agent in oil well drilling
mud, which accounts for about 90% of consumption, in barium com-pounds,
in paints, in glass, in paper fillers, and in refining sugar. Freight
rates are high and barite being a dense, heavy mineral of relatively
low unit value, the distance from producer to consumer is economically
critical. For current prices contact the Arizona Department of Mines
and Mineral Resources.
Arizona has produced approximately 1% of the over 30 million tons of
barite mined in the United States since 1882. The first commercial barite
productions came from Cochise County in 1925. From available records
it is estimated that Arizona's barite production between 1929 and 1955
was about 317,000 tons. Close to 312,000 tons came from the veins of
the Granite Reef (aka Arizona Barite or Macco) mine, Maricopa County
between 1931 and 1955. Eight other mines in five counties yielded the
other 5,000 tons. Since 1986 there is no record of barite production
in Arizona. The standards of quality vary by use. A barite product for
drilling mud must have a mini-mum specific gravity of 4.25 (about 92%
BaSO4) and at least 90% of the product must be ground to minus 325
mesh. Many other uses require a product that is 95-98% BaSO4 with no
more than minor amounts of iron oxides, silica and alumina.
In 1979 Nevada continued to be the largest producer with 82.5% of the
total, followed by Missouri with 7.4%. Other producing states were
Arkansas, Georgia, Idaho, Illinois, Montana, and Tennessee. The average
price per ton, f.o.b. mine in 1979 was $22.93. This is over $2.00/st
higher than the 1978 average.
In 1999 well drilling consumed over 94% of the barite used in the
United States. Imports and domestic production for the year totaled 1.4
mil-lion tons. Nevada remains the largest U.S. producer but production is
about one third of the 1979 level due largely to low-priced imports of
barite. China supplies most of the imported barite; domestic production
was only 33% of the total. The average price per ton was $25.58.
The Arizona Department of Mines and Mineral Resources has numerous
references on the geology, mineralogy, mining and processing of barite,
and, in the museum, specimens for examination.
|
