On a date with a geologist - Date 4, part 1.

 

Wall made of local stone at The Cloisters. 

Date four was amazing! We traveled to various locations in Eastern America and saw a lot of rocks. We spent a day checking out The Cloisters, a museum dedicated to Medieval art in New York to satisfy my other interests. The museum overlooks the Hudson River and is composed of three reconstructed cloisters acquired from various areas in Europe as well as a great many artifacts and artworks from the 12th - 15th century. The buildings are based in a beautiful park land and feature both imported and local stone. One of the beautiful rocks used for the carpark walls is a local garnet schist. It has undergone significant metamorphism and shows bands of garnets as well as aluminosilicates.

 

Garnet in the schists

We did take a moment or two to head out onto a balcony and take some happy snaps of the river, the bridge we crossed onto the island over and of course, each other. Out here we discovered some interesting things.

 

The river.

Part of The Coisters are clad in micro-granite blocks. I do not know if they are local but given the presence of the schist, it stands to reason there was once a local subduction zone so there should be some local granites forming. Some of these micro-granite blocks feature lovely aplites dykes as pictured below. Aplite is a fine grained intrustive rock composed of quartz and feldspare (thus the pink colour). It is often produced as the final spurt of melt which fills in / takes advantage of small cracks in the rapidly cooling batholith.

 

Aplite dyke in a micro-granite blocks.

The balcony has also been crafted of local stone and displays a rather lovely meta-psammo-pelite aka gneiss. Below is a photograph of a rather lovely specimen showing dark and light banding.