In the area of the upcoming Dobra gneiss, an orthogneiss, which is the oldest rock in Austria at an age of 1377 million years, developed in the fading of the “Variszian mountain formation” between about 300 to 250 million years ago today, by relieving pressure cracks and columns ( “cracks”). The fluids circulating in them were rich in silicic acid and, upon cooling, deposited quartz on the walls of the fractures. Where these were not completely filled the gaps, there was room for beautifully formed quartz crystals, such as those shown in the special show.
from Thursday, March 22, 2018