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The Mt. Montro kyanite deposit, Grand Bassa County, Liberia

January 1, 1968

The Mt. Montro kyanite deposit, 14 miles north of Buchanan, Grand Bassa County, Liberia, is near the middle of a belt of kyanite-bearing gneisses and schists that is 9 miles long and 1 mile wide. The deposit, which seems to be the most persistent and the largest single body of kyanite rocks in the belt, is approximately 12, 600 feet long, as much as 480 feet in outcrop width, and from 25 to 350 feet thick. Kyanite-quartz-biotite-feldspar-garnet-muscovite gneiss, local interbeds of kyanite-mica schist, and lesser amounts of biotite-quartz gneiss, are the principal rocks in the deposit. Other rocks in the kyanite belt include garnet-biotite gneiss, undifferentiated quartzo-feldspathic gneiss, quartzite, and amphibolite. The rocks are the product of regional metamorphism to almandine amphibolite facies. The regional strike is northwest and dips are southwest.

Kyanite crystals are as much as 3 inches long. The kyanite content ranges from 5. 8 to 46. 7 percent, but most rocks contain between 10 and 35 percent. Garnetiferous beds contain as much as 15 percent red garnets that range to half an inch in diameter. In general, the garnet-rich beds are found in the upper part of the deposit.

he total reserves of the Mt. Montro kyanite deposit are estimated at about 10 million tons of kyanitic rock containing approximately 2.5 million tons of kyanite. These estimates include measured, indicated, and inferred reserves, calculated to depths of 25 to 100 feet, on the assumption that open-cut mining to those depths would be feasible. The largest part of the deposit underlies Mt. Montro and contains about 8 million tons of kyanitic rock containing nearly 1.9 million tons of kyanite. Residual soil overlying the deposit averages about 5 feet in thickness and is estimated to comprise slightly more than 400,000 cubic yards of material containing about 186,000 tons of kyanite.

The proximity of the kyanite deposit to a paved highway, to port facilities at Buchanan, and to water, electrical power, and timber resources are considered favorable factors relevant to possible development.

Publication Year 1968
Title The Mt. Montro kyanite deposit, Grand Bassa County, Liberia
DOI 10.3133/ofr68258
Authors S. Anthony Stanin, Bismark R. Cooper
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 68-258
Index ID ofr68258
Record Source USGS Publications Warehouse