| A study of the geographic and geological features of northern Puerto Rico that gave form to high-purity quartz sands was conducted. These occur as superficial accumulations of 98% to more than 99% silica, with very low iron and clay content. The study covered the coastal plains and karst belt of northern Puerto Rico from Aguadilla to Loiza, where all high-purity quartz sands are found. Characterization of selected deposits consisted in surveying, transecting, soil drilling, outcrop study and aerial photo evaluation. Soil boring logs and thickness contour diagrams were produced for previously mapped and newly discovered deposits. Original surface areas and thickness vary up to 12 square kilometers and 330 centimeters respectively. Quartz grain surface texture analyses using scanning electron microscopy suggest river and shallow marine transport, as well as soil-forming processes. Quartz grain size parameters indicate good sorting and unimodal distribution, having a high proportion of grains in the 1&phis; to 3&phis; (0.5 to 0.25mm) size range, and modes in the 2&phis; to 2.5&phis; range (fine sand). The final character of the quartz sands form by residual concentration from the quartz-rich Quaternary, marine-deposited source sediments. Results indicate that by July of 1998, existing quartz sand yields were estimated in 15.8 million tons. Of these, only about 2.3 million tons were in extractable, scattered deposits. The glass industry needs to explore different sources of raw material and promote the recycling of glass products. |
