Minerals and Igneous Rocks

In-class lab activity

Back to the GEOL 241 Homepage


In this in-class lab activity you will (1) examine the most common rock-forming minerals and their properties (e.g. hardness, cleavage, etc), and (2) examine and classify intrusive and extrusive igneous rocks.

To prepare for our meeting you might want to review the chapters on minerals (CH 3) and igneous rocks (CH 4) from this online and free introductory geology textbook: An Introduction to Geology from Salt Lake Community College.

Lab Handouts

I will provide you with the lab handouts at our meeting but in case you want to look at a clean copy here they are: Minerals lab handout; Igneous Rocks lab handout.

Making a Connection

Studying mineral samples in a lab setting is obviously very interesting. However if you are not careful it's easy to just think of the sample in your hand rather than the occurrence of minerals within the whole earth system. A lab sample of a mineral is "small". On the opposite end of the spectrum, something that is "large" might be a lithospheric plate! Can we make a connection between these two ideas?

The Creeping Section of the San Andreas Fault

Hollister, CA, is famous for being along the creeping section of the San Andreas Fault. Hollister is actually on the Calaveras Fault, which splits from the San Andreas Fault near Hollister -- so we might think of this region as a fault zone. Creeping means that offset along the fault is accommodated in a more continuous manner rather than the fault accumulating strain and then releasing it all at once in an offset. Below are some links giving an overview of this idea, focusing on the Hollister area:

It's not difficult to start thinking there must be some interesting rock-physics going on with creeping fauts:

Finally, here is a study that makes a connection between creeping faults (at least for the example along the San Andreas Fault) with minerals -- which is where we started our story:

What is the connection made in this paper?


Due at the next lab meeting.

Write a short summary of (1-2 concise/lean paragraphs):