DEPTH AND PARTICLE SIZE DISTRIBUTIONS OF TALC IN A VIRGINIA PIEDMONT ULTISOL

Talc is a constituent ofmany hydrothermally altered ultramafic rocks and thermally metamorphosed do-lomites (Deer et aL, 1962), but it has rarely been de-tected in soil profiles (Zelazny and Calhoun, 1977). Talc was detected in soils directly overlying a talc de-posit in southeastern Pennsylvania (Blount and Spohn, 1982), along with serpentine, chlorite, illite, tremolite, plagioclase, quartz, and interstratified phyllosilicates. The mineralogy of the latter soils is atypical of residual humid region soils, which are commonly high in ka-olinite and other secondary minerals associated with a leaching and acidic environment. The scarcity of talc in soils has been attributed to instability in a leaching environment (Reiche, 1943); however, we have detected this mineral in a highly leached Virginia Piedmont Ultisol formed over deep saprolite. This study reports the depth and particle-size distribution of talc in this soil profile which, by traditional concepts of mineral stability, is an unlikely environment for such a phase