Figure 1. New Caledonia geology map.
I recently used QGIS and Inkscape to make a geology map of New Caledonia for my M.Sc. thesis. Thankfully I can read enough French to find things like the official French government sanctioned geology Shapefile online [1].
Figure 2. Layout & symbology in QGIS.
First, I imported the geology polygons into QGIS and set up the symbology to my liking. I wanted to make a greyscale map because eventually I plan on publishing, and some journals require lots of money to publish colored images. I had 6 undifferentiated geologic units to map, but there are only 5 good greys (0, 30, 60, 80, 100% black). Therefore one of my units had to be a pattern. I chose to make the metamorphic terranes diagonally striped parallel to the foliation (Fig. 2). I made a legend in MS Word using a table (Fig. 3).
Figure 6. Inkscape layers to make a patterned mask.
The problem is that when I exported the image from QGIS, the pattern did not export properly at all (Fig. 4). So I re-exported the geology map as two images: (1) with blank polygons in place of the patterned polygons, and (2) with blank polygons for everything but the MM terranes, and the MM terranes in black, which I then inverted in GIMP (Fig. 5) so I could use it as a mask in Inkscape (Fig. 6). I made a square mask for the MM unit in the legend and grouped it (CTRL+G in Inkscape) with the MM terrane mask. Then I hid the mask while I created striped pattern under it using stroke/fill on a rectangle, which I duplicated to use in the legend. I applied the mask (Object -> Mask -> Set in Inkscape; Fig. 7) and voila (Fig. 1). Beautiful.
References
[1] Direction de l’Industrie, des Mines et de l’Energie and Service de la Géologie de Nouvelle-Calédonie, Bureau de Recherches Géologiques et Minières, 2011, Carte de la géologie de la Nouvelle-Calédonie, scale 1:1 000 000: http://sig-public.gouv.nc/Geologie_1000000.zip (Aug 2011).
Runs with Rocks 
