Sandsten och kvartsit med flusspatcementerade kvartssfäroider

Abstract

Summary Sandstone and quartzite with fluorspar cement A gray sandstone and a dark blue quartzite of Lower Cambrian age from around Kyrkberget in southern Swedish Lapland contain large quantities of small white spheroids. This is specially apparent in the dark quartzite (Fig. 1). The spheroids consist of quartz, cemented with fluorspar. The quartz occurs partly in larger, rounded grains, partly in smaller, edged grains. The fluorspar is seen to fill all open spaces between the quartz grains (Figs. 2 and 3). In some cases a reiterated cementation of fluorspar occurs in an outer ring of the spheroids outside a zone of unaltered quartzite (Fig. 4). An analysis of fluorine in the rock, as seen in Fig. 1, gave 5,98% F corresponding to 12.21% fluorspar. The spheroids are assumed to represent parts of the rocks, which originally have had an aggregation of less compact portions which have been more receptive to mineralization. The angular grains of quartz in the spheroids may be ascribed to corrosion by fluorine.