The harder a rock or mineral is, the more it holds up to erosion. The diamond is the hardest mineral known, and therefore holds up to erosion the best. A common mineral that makes up vast amount of the rocks on earth’s surface is quartz. Topaz and Corundum are even harder, but more rare. The hardness of a mineral, whether it be in a rock or on its own is a way for geologists to determine what they are (as color can be very misleading at times). How easily a mineral can be scratched is a way to determine its hardness.
The hardness of a mineral is not really a measure of how well a rock withstands erosion. Diamonds themselves might not suffer much erosion, but the rocks containing them certainly will, and when they break up the diamonds in them will be transported elsewhere. That’s why there are diamonds (and gold nuggets) in the glacial debris of Indiana – they came there after the rocks in Canada containing them were eroded to sand, pebbles, and silt by rivers, and then glaciers moved them further.
Rocks that survive the best under erosion are those that are solidly cemented together, have little pore space for water to get in (freezing and thawing are great mechanical breakers of rocks), and are made of minerals that are relatively stable under pressure and temperature conditions at the earth’s surface. A mineral that in and of itself is very hard may be quite unstable under surface conditions. Feldspar is a good example, hardness just less than quartz, but often with chemical zonations, included minerals, and so on that enhance its erodibility so that it changes fairly easily into clays. Likewise granite, ostensibly a pretty hard rock, often falls apart very easily under surface weathering conditions.
Click here to cancel reply.
Sorry,At this time user registration is disabled. We will open registration soon!
Don't have an account? Click Here to Signup
© Copyright GreenAnswers.com LLC