Amendment

I have recently begun to have serious doubts about whether all those rocks I have been calling pegmatite were not in fact simple granite. The only ones I know for sure are pegmatite are those from the excursion to Väddö, where the teachers explicitly identified them as pegmatite. The rocks I have found in the forest around my home were similar in colour and had pretty large grains – pegmatite is mainly distinguished from granite by its extremely coarse grains – so I called them pegmatite without more thought to it.

But, eventually, I came to wonder whether those grains really were that large. I recall vaguely that a pegmatite has a grain size of about 2 cm or more. I checked with some sample rocks I have collected, and their grains are closer to 2 mm. Moreover, I read now that pegmatite usually appears as an elongated tongue (it is a gångbergart – a Swedish term referring to igneous rocks that readily form in subterranean tunnels), while granite is more common as massive chunks like the ones I have seen in the forests.

Thus, I wish to announce the following amendment: all rocks I have identified as pegmatite since the excursion to Väddö are most probably actually granite. My sincerest apologies for the misconception, and for any troubles it might have caused. Errare humanum est…