Geologic report series 15

Crushed marble samples from two quarries in Franklin and Sparta, Sussex County, were analyzed for amphibole content using x-ray diffraction. Regulatory asbestos fiber content was measured using light microscopy. Respirable amphibole fiber content was determined using electron and light microscopy. Cadmium and zinc were measured using atomic absorption. Total amphibole content ranged from 0.1 to 0.9 percent by weight. Regulatory asbestos fibers were measured at 16.9 and 42.0 fibers per milligram in pulverized marble samples from the quarries in Franklin and Sparta, respectively. Respirable amphibole was measured by light microscopy at 9.6 and 7.6 regulatory fibers per milligram in the same respective samples. A substantial amount of amphibole fiber was also found in worn and weathered gravel composed of marble. Observations under light and electron microscopes indicate that most of the fibers in the crushed stone samples are derived from prismatic to acicular amphibole. Amphibole of semiasbestiform to asbestiform habit accounts for a small but discernible portion of the total fiber content. Most fibers are the result of cleavage, although there is some evidence for fibrillar development in some of the amphibole. Habit-type is important in interpreting the data on amphibole content presented here. Most of the amphibole fibers noted, although considered asbestos for regulatory purposes, are derived from amphibole which does not meet mineralogical or commercial criteria for asbestos, and which cannot be equated with asbestos in physical or biological terms. In interpreting actual asbestos content, content of fibers of aspect ratio greater than 20 seems to be a more reasonable criterion than content of fibers above the regulatory limit of 3. Average cadmium concentration in Sparta crushed stone samples was relatively high, about 660 ppb. At Franklin, cadmium is much lower, averaging about 67 ppb. Zinc averaged 111 ppm at Sparta and 26 ppm at Franklin. Sphalerite and aragonite were identified as cadmium-bearing mineral species in the stone. Cadmium in pulverized carbonate rocks bears further study as a source of cadmium in soils to which such limestones are applied.This series has at times has been entitled Geologic report series, Geologic report (Trenton, N.J.), and ultimately Geological survey report (Trenton, N.J.)