Big feldspars

For the non-scientists among you (shame on you) this is simply part of my fireplace. For the geologists in the audience, this is a piece of a big-feldspar dyke from the Gardar Province, West Greenland. I collected this as part of my Honours degree project in the summer of 1978. When I found this on my mapping area, I thought that I had discovered a new rock-type! When I got back to base-camp and read the papers on this area I found that it had been discovered long before and is called the Big Feldspar Dyke suite! The plagioclase feldspars (the white rectangles) were crystallising and floating in the magma of the Andesite lava (the dark stuff) and growing enormously big in the melt as they did so (5p piece for scale). Ah, those were the days!