Comparison of color, chemical and mineralogical compositions of mine drainage sediments to pigment

Forty-three untreated and actively and passively (wetland) treated coal min e drainage sediments and five yellow-red pigments were characterized using X-ray fluorescence, fusion-inductively coupled plasma atomic emission spect roscopy, Xray diffraction, and tristimulus colorimeter. Primary crystalline iron-bearing phases were goethite and lepidocrocite, and iron phases conve rted to hematite upon heating. Quartz was nearly ubiquitous except for synt hetic pigments. Gypsum, bassinite, calcite, and ettringite were found in ac tive treatment sediments. Iron concentrations from highest to lowest were s ynthetic pigment>wetland sediment> natural pigment> active treatment (untre ated sediments varied more widely), and manganese was highest in actively t reated sediments;loss on ignition was highest for passively treated sedimen ts. No clear trends were observed between quantified color parameters (L-st ar, a(star), b(star), and Redness Index) and chemical compositions. Because sediments from passive treatment are similar in chemistry, mineralogy, and color to natural pigments, the mine drainage sediments may be an untapped resource for pigment.