Boulder trail – gneiss

Gneiss is a metamorphic rock, meaning it has been altered by heat and pressure deep within the Earth. Gneiss resembles granite but is distinguished by its unique striped or banded appearance. There are many types of gneiss, often named after the minerals they contain. This specific type is called feldspar gneiss due to its abundance of feldspar, one of the most common minerals in the Earth’s crust.

This rock’s crystals are fine-grained, meaning they are so tiny that you may need a magnifying glass to see them. Feldspar itself appears in light tones, such as white or pinkish-red, forming the lighter stripes in the gneiss.

Did you know that some of the gneiss found in Greenland are the oldest rocks on Earth, dating back up to 4 billion years?

Task: Look at this rock closely! Can you see the differently colored minerals? What are more abundant in this rock: the darker or lighter spots (minerals)?