Boulder trail – migmatized gneiss

Migmatized gneiss is a type of metamorphic rock that forms when heat and pressure deep within the Earth begin to alter existing rocks. In some cases, parts of the rock even start to melt slightly. When gneiss partially melts, it transforms into a new rock called migmatite. The term “migmatos” comes from Greek, meaning “mixed”. Migmatised gneiss indeed resembles a blend of rocks. Its appearance features light and dark bands intertwining like beautiful stone ribbons.

It can sometimes be difficult to distinguish between gneiss and migmatite, as they can look very similar. Kalevipoeg’s legendary slingstone, a famous glacial erratic near Prossa lake, is a migmatite rock type.

Migmatized gneiss is appreciated for its decorative appearance, with alternating light and dark stripes forming intricate patterns.

Task: Observe this rock closely, focusing particularly on its polished surface. Can you see the light and dark bands? Pick one stripe and try to trace it around the rock with your finger – does it lead you back to the same spot?