Petrological and Chemical Characterisation of High-Purity Quartz Deposits with Examples from Norway

Abstract

Demand for high-purity quartz (HPQ) is strongly increasing worldwide owing to growing consumption and an increasing range of high-technology applications. This study includes: (1) a refined definition of HPQ (2) a discussion of the impurities controlling the chemical quality of HPQ products and (3) descriptions of selected HPQ deposits in Norway, both economic and potentially economic examples. The suggested definition of HPQ proposes concentration limits for the most important detrimental elements. The maximum content of each element should be: Al <30 μg g−1, Ti <10 μg g−1, Na <8 μg g−1, K <8 μg g−1, Li <5 μg g−1, Ca <5 μg g−1, Fe <3 μg g−1, P <2 μg g−1 and B <1 μg g−1 whereby the sum of all elements should not exceed 50 μg g−1.Impurities within quartz crystals (intracrystalline impurities) control the quality of HPQ products because they cannot be removed by conventional processing. These impurities include (i) lattice-bound trace elements, (ii) submicron inclusions <1 μm, and (iii) mineral and fluid micro inclusions (>1 μm). Present knowledge about intracrystalline impurities in natural quartz is described. The methods used here for identification and analysis of impurities are backscattered electron (BSE) and cathodoluminesence (SEM-CL) imaging and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The HPQ deposits discussed include the Melkfjell quartzite, several kyanite quartzites, the Nedre Øyvollen pegmatite and the Kvalvik, Nesodden and Svanvik hydrothermal quartz veins. The discussion focuses on the content of lattice-bound trace elements and the micro-inclusion inventory because these are the major parameters which determine the quality of HPQ products. Finally, processes leading to HPQ formation are discussed.