
Figure 12
The `spheric' or `stereographic' projection of a vesuvianite crystal according to Neumann (Neumann, 1823, Table IV). Each crystal facet is symbolized by a tiny roundel  the dots of Fig. 11  either upon or inside the projection circle. The roundels of one and the same `zone' all lie either upon that circle, or upon an ellipse of varying width. For simplicity's sake these ellipses are represented by cutting arcs of a circle. 