INVESTIGATION OF MINE WASTE FROM A KYANITE MINE IN VIRGINIA: A CASE FOR WASTE RECYCLING

Kyanite mining corporation, Dillwyn, Virginia has been in operation for over 50 years and their local operation is the largest kyanite mine in the world. As part of the processing at this location, mine waste is separated into three waste streams, a purified quartz-rich sand, a magnetic separate and a pyrite separate. The pyrite separate is sold as a mineral commodity and the purified quartz-rich sand is sold locally. Several tons per day of the magnetic separate are generated and a preliminary minimum estimation of 50,000 tons of waste has accumulated. Currently no use for the magnetic separate has been identified. We investigated eight representative samples of the magnetic mine waste which varied in color from a dark tan to black to determine if the waste could be recycled as an ore or could be used as an environmental media.

Mineralogical investigations indicate the composition of the mine waste is dominated by magnetite, kyanite, lesser amounts of hematite and charcoal. Magnetite occurs as fine grained crystals and as inclusions in kyanite. Hematite occurs largely as botryoidal textures as both discrete grains and coatings on kyanite grains. Fe-oxide spheres ranging in diameter from approximately 100 to 5 micrometers are common and may compose up to 10% in some samples. Titanium dioxide was rarely observed as coatings on kyanite grains. EDS analysis on magnetite crystals indicates they have end member compositions. Bulk property investigations indicate that grain size distribution of samples is primarily unimodal with 20 to 40 percent of material being between 0.600 and 0.250 mm. Coefficients of permeability of samples investigated vary between 0.0036 cm/s to 0.0077 cm/s and are consistent with permeability expected of sands with similar grain size distributions.

Economic parameters likely prevent this material from being used as an Fe or Ti ore. This investigation indicates that the magnetic waste stream may be environmentally benign and may be suitable for use as an environmental media in constructed wetlands, sand filter traps, and as an aggregate additive.