Climbers guide microgranite and pegmatite скачать в хорошем качестве

Climbers guide microgranite and pegmatite

Microgranite (aka aplite) and pegmatite often occur in close association. This is true at venues such as Binnein Shuas, which is described as microgranite in the guidebooks but the granite sectors of the crag are over 50% pegmatitic. So what is the difference? Microgranite has a grainsize smaller than ~2 mm whereas pegmatite has a grainsize over ~2 cm. That means they climb very differently, with microgranite tending to have good friction and rounded holds. Pegmatite by contrast tends to be rough at the scale of the crystal size, but individual crystal surfaces can be very smooth so you end you with a paradoxically slippery rough rock. To learn about the aplite pegmatite associateion check out the "double pegmatite dyke" video:    • Double Pegmatite Dyke: Coire an t-Sneachda