On rosenbauschite

Rosenbuschite is one of the numerous mineral species named by Brøgger (1887) and described in full detail in his great work on the minerals of the syenite-pegmatites of southern Norway (1890). This rare mineral occurs in sparse pale-orange patches of close-packed parallel to divergent fibres and needles embedded in coarsely crystallized pegmatite at Langesundsfjord. From the straight extinction of the fibres and such meagre goniometric measurements as were possible on this unfavourable material, Brøgger concluded that rosenbuschite is monoclinic, elongated with the symmetry axis. Taking the plane of cleavage paraBel to the needle-axis as the base, and naming the observed forms c {001}, a {100}, s {201}, h {540}, Brøgger obtained geometrical elements somewhat similar to the accepted monoclinic elements of pectolite and wollastonite. Analyses on limited material revealed a complex composition which Brøgger interpreted as essentially a fluo-silicate, zirconate and titanate of lime and soda, of metasilicate type. These crystallographic and chemical findings appeared to form a firm basis for accepting rosenbuschite as a zirconpectolite and appending it to the wollastonite group, which was regarded as a part of the wider group of the pyroxenes. Since the appearance of Brøgger's work no direct observations on rosenbuschite have been recorded.