8.3: Assignment- Metamorphic Rock Lab

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Module 8 Assignment

Metamorphic Rock Lab

Figure 1. Shiny Vishnu Schist in the Grand Canyon. The Vishnu Schist is a metamorphic complex that forms the basement rock of the Grand Canyon. It is a little over 1.7 billion years old.

Overview

You can start the activity after you have completed the reading assignment.

In this lab, you will study photos of several metamorphic rocks and determine their physical properties.

Instructions

A. Before you begin this activity, you may also wish to review the Metamorphic Rock Identification page. Some optional resources you can use are:

B. Select each photo below to view the igneous rock samples larger. You can also view the images in Flickr by clicking the link, and zoom in on each of these samples in the picture to get a better view of their texture:

Select an image to view larger

Figure 2. Red slate (5.8 cm across at its widest).

Figure 3. Marble from the Miocene of Colorado, USA. (6.2 cm across at its widest). The specimen shown above is from the Yule Marble, the state rock of Colorado, quarried near the town of Marble, Colorado, USA. Yule Marble formed by contact metamorphism of the Leadville Limestone (Mississippian). The igneous intrusion that metamorphosed limestone into marble is the Treasure Mountain Granite (Middle Miocene, 12 Ma). – James St. John

Figure 4. Quartzite (metaquartzite). Quartzite is a common, crystalline-textured, intermediate- to high-grade metamorphic rock. It forms by metamorphism of quartzose sandstones or siltstones. Quartzite can be entirely composed of interlocking quartz crystals, or the original sand grains may still be visible. This rock is hard (H = 7), will not bubble in acid (unlike marble), and can be almost any color.

Figure 5. Gneiss. Gneiss is a high-grade, foliated metamorphic rock. It differs from lower grade foliated metamorphics, such as slate, phyllite, and schist, by having alternating bands or stripes of light and dark minerals. Metamorphism has been so intense that minerals have self-segregated into discrete zones. Most gneisses form by metamorphism of schists or granites..

Figure 6. Muscovite Schist. The muscovite schist shown above is a common variety of mica schist.

C. Determine the following characteristics to the best of your ability from the photos of the samples above:

Color
Texture (foliated or non-foliated?)
Probable mineral content
Probable parent rock
Was this rock a product of low-, medium-, or high-grade metamorphism?
Compare your personal observations with the information in the course Rock and Mineral Guide (above). How is each sample different (or similar) from the Guide?
For one of the rock samples of your choice, write a half-page summary describing the physical characteristics you can determine from the photo or from any personal sample you have collected. If using a personal sample, please include a photograph. For all the other samples above, include a table summarizing the characteristics you observed (1 – 6). You will be graded on this activity as described in the rubric below.

Grading Rubric

10 points: Report accurately summarized the metamorphic rock characteristics, spelling and grammar are correct and complete sentences are used, including a photograph. Characteristics of the other samples are included in a table and are accurate.

8 points: Report mostly captured the metamorphic rock characteristics, spelling and grammar are mostly correct and complete sentences are used, including a photograph. Characteristics of the other samples are included, but one or two details were missing.

5 points: Report missed two or more characteristics, included spelling and grammar errors, and/or did not include a photograph. Characteristics of the other samples are included, but over half of the samples and/or characteristics are missing.

2 points: Report was inaccurate, included significant spelling and grammar errors, and/or did not include a photograph. Characteristics of the other samples are not included.

0 points: Did not complete the assignment.