T157 Environmental Geochemistry for Modern Mining

Tuesday, 2 November 2010
8:00 AM - 12:00 PM
Room 601

MINERALOGICAL AND GEOCHEMICAL INVESTIGATIONS OF THREE WASTE STREAMS FROM A KYANITE MINE IN CENTRAL VIRGINIA: IMPLICATIONS FOR RECYCLING IN AN ECONOMICALLY DISADVANTAGED REGION

Paper number: T157-13
Program: Technical Sessions
Time: 11:00 AM – 11:15 AM

Authors

Abstract

Waste streams from a kyanite mine in Buckingham County, Virginia were investigated to assess recycling potential. Currently kyanite ore consists of approximately 20% kyanite, 3% pyrite waste, 7% magnetic waste and approximately 70% silicate-rich waste. An estimated 382,000 tons of the pyrite waste stream has been generated over the past 60 years. The mineralogy of this waste stream consists of variable amounts of pyrite (70 to >99%), talc (1 to 20%), quartz (1 to 10%), kyanite (0.5 to 5%) with minor or trace amounts of magnetite, hematite, galena, anorthite and rare earth phosphate. Bulk chemical analysis indicates that Zn (28 to 367 ppm), As (8 to 18 ppm), Se (44-64 ppm), Cd (0.19 to 1.03 ppm), Hg (0.87 to 35.91 ppm), and Pb (65 to 189 ppm) occur at levels of some environmental concern. Au and Ag concentrations are negligible. Currently the waste stream is well managed and sold, but for a low price. Talc is of sufficient quality to be of interest for recycling and pyrite may be suitable for recycling in the future for solar energy technologies.

The silicate-rich waste stream currently accumulates at an estimated rate of 450,000 to 600,000 tons per year and with an estimated 27 million tons having been produced since operations began. Several elements of environmental concern (V, Cr, Ni, Cu, Zn, As, Ag, Sn, Sb, Ba, Hg, Tl, and Pb) were detected, however only Ni occurred at concentrations above background levels of the kyanite schists of the region. Muscovite is a common constituent of the waste and is suitable for recycling in pigment applications. The waste has significant potential for recycling as constructed wetland media for the region.

The magnetic waste stream has accumulated an estimated mass of approximately 3.6 million tons and dominantly consists of magnetite, minor pyrrhotite, hematite, kyanite, and charcoal. Elements of environmental concern (e.g., Cu, Zn, Pb) do occur and are largely in low solubility oxide phases. If a specialized steel market could be identified the waste could be recycled as iron ore.

New infrastructure would be needed to recycle the waste streams. Recycling of all three waste streams may reduce financial risk compared to recycling any individual waste stream. This investigation illustrates the importance of integrated mine waste investigations in economically disadvantaged regions.