SANDSTONE!!!!!!

Sandstone is a sedimentary rock made up of the minerals quartz and/or feldspar. The clear quartz and amber feldspar create a brown, yellow, or red color But not in this specimen which was glued on the board at the beginning of the neglected "Geology Walk" in the NYBG forest. That hurts my head.

Besides being called a Sedimentary rock it is also called a Clastic rock. This means that the sedimentary materials are made up of older broken up pieces of rock.

They are formed by layers of sand and mineral deposits (under water or on land) covered by other sedimentary layers or rocks. The pressure from this forces causes them to compact and cement. Silica and calcium carbonate are usually the binding agents. I don't know where they came from. This also hurts my head.


Antelope Canyon, Navajo Reservation, Arizona

I was surprised to read that some sandstones are not as susceptible to erosion as their sedimentary brothers and sisters. This is because of the hardness of the individual grains and the uniformity in their size. Yet, somehow, it is easy to work with to make buildings and other structures. As I'm sure everyone knows it is highly friable. Such a word and it only means "easily crumbled". Apparently this makes it an ideal material for a grindstone or knife sharpener.


Hawa Mahal, Rajasthan, India

I am going to assume that different varieties of sandstone are a result of different feldspar/quartz ratios, amount of pressure, heat variations and the atmosphere in which they were made and have emerged.

So, to recap, it's easily broken and made up of broken pieces of older rock, yet slow to erode and hard enough to sharpen a knife and grind stuff.

Very moody rock.

The sandstone layers in the Grand Canyon, being more resistant, form the cliffs while the shales and siltstones, easily giving way to weathering and the scouring from the Colorado River, form as slopes.