Shale Nature Study – Rock Update #2

Our local landscape is full of rocks…the area was settled by gold miners in the California Gold Rush and even today there are gold mines in our area that are back into production (the price of gold is up enough that they can make money). There is a park in our neighborhood that has an exposed bank next to the road and that is where we found our shale to study as part of my on-going year-long focus on rocks.

This is our official first rock from the list which we pulled from the book Rocks, Fossils and Arrowheads (Take-Along Guides). See last month’s entry for my preparation for this project where I will be attempted to locate and collect as many of the rocks from the book as  possible during 2013: Rock Update.

This is what our local shale looks like….like wafers that are either horizontal or vertical. The color varies but mostly the out-croppings we have seen are light colored from a light gray or red or even green. Doing some research has revealed that it is the organic materials in the shale that give it its color: iron oxide, hematite, geothite, or mica.

This is the piece of shale that is shown sticking out in the photo above. I could just slide it out.

Shale is a sedimentary rock that is mostly composed of clay and is sometimes called mudstone. It can easily be scratched with a knife and has a quality that is listed as “laminated”. This means that the rock is made up of many thin layers.

The mystery rock from last month’s entry turns out to be slate which is the metamorphic form of shale. Guess what next month’s rock will be? You guessed….slate! I will explain how you can tell the difference because in the process of identifying the shale I also learned quite a bit about slate.

You can read all my 2013 nature study goals here on my blog.