Field/Lab Assignment

Part IBy: Roberto Vargas

The first rock is a sample of basalt, which is a type of Igneous rock. Basalt is a type of igneous rock that forms at Earth’s surface so it is an extrusive igneous rock. This sample was a dark green colored rock and is full of silicate minerals that contain a high amount of iron and magnesium. I found this rock while heading up to Parkfield, California. It was next to a really big rock which seemed to be basalt as well.

This rock sample is a type of Metamorphic rock. I believe it is Gniess. This rock sample seemed to have gone through regional metamorphisim, which means that the crystals recrystallized with the orientation that is perpendicular to the direction of the compressional force. This gave the sample a sort of layered appearance or a foliated texture. I decided that this was a metamorphic rock because it clearly looked to me like this rock had changed its form.

My third sample was an igneous rock. I believe this rock is granite. I believe this is grantie becaue of its texture and light colors. This is an intrusive rock that has a coarse-grained texture. This rock has silicate minerals quartz and feldspar. This type of rock is a major component of continental crust. I found this around Slack Canyon when I went on a field trip during the summer. This type of rock is mostly found to the west side of the San Andreas Fault.

This rock sample is a sedimentary rock. I believe this is a limestone sample. This is a chemical sedementary rock which means that it was formed when material dissolved in water percipitates. This type of rock is mainly composed of the mineral calcite. I found this rock close to where I live near a creek.

This rock sample is another igneous rock. This is a”plug” of basalt that is found on the Parkfield Road. Like my first sample this Basalt is alsoand extrusive igneous rock because it forms at Earth’s surface. It had a dark green color to it and like I mentioned it is located along the Parkfield road between the Fresno and Monterey county line and the Castle Mountain fault. I was really intriguid by this one because I would have never even thought that something this big could be basalt.