The Beorgs of Uyea are formed from granophyre - a type of granite made of the minerals potassium feldspar (which gives the deep red colour), white quartz and black biotite mica. It formed about 360 million years ago as molten magma cooled beneath the ancient Caledonian Mountain chain. In places the granophyre is cut by sheets of riebeckite felsite - a particularly attractive igneous rock. The felsite formed from magma that exploited cracks in the granophyre and then cooled so quickly that there was no time for crystals to grow. Instead the magma solidified as pitchstone - a kind of natural glass in which the atoms were arranged irregularly rather than in orderly crystal lattices. Over time, random atomic movements allowed some atoms to shuffle into a more regular alignment. Each point where this happened created a nucleus around which crystals slowly grew outwards until the glass had entirely crystallised. This process is known as spherulitic devitrification. It resulted in a rock with circular patterns of crystals which are exposed clearly when the rock is polished. In places a flow-banding pattern formed when the magma entered small fissures within the granophyre and the crystals aligned themselves in parallel.
These dykes were exploited during the Neolithic period to create polished ceremonial knives from the beautiful riebeckite felsite.
Directions
Uyea is in the North Mainland to the west of North Roe
Take the A970 to North Roe and park near the school
Walk along the road until you pass North Haa Road then take the next track on your left which leads out to the northwest coast
After about 2.5 km you will see Pettadale Water to the north of the track. The site is just west of Pettadale Water and south of the track
Please note that about two hours are needed to walk to the site and back