LAB 1 - Ge 101
Fall Quarter 2013
Name______Time to complete:______hours
Specimen 1. Olivine
Chemical formula:
Sketch:
Scale x_(i.e., “times” what factor as drawn?)______
This rock is a xenolith (“foreign rock”) preserved in basaltic lava, delivered to the earth’s surface from the mantle, composed entirely of olivine grains. They don’t generally show crystal faces, and so are anhedral (“no faces”).
You should also see black and grass-green grains, these are two varieties of the same mineral group, any guesses as to which one? ………………………………………….
Specimen 2. Pyroxene (variety: augite)
Chemical formula:
Sketch:
Scale x______
In your sketch, try to orient it and annotate the sketch to show two cleavage planes at 90°.
Specimen 3. Plagioclase (variety: labradorite, Ca-rich)
Chemical formula:
Sketch:
Scale x______
Can you recognize the blue, iridescent schiller, and the high-luster cleavage planes? Try to identify two cleavage planes at right angles.
Specimen 4. Plagioclase (variety albite, Na-rich)
Chemical formula:
Sketch:
Scale x______
Try to make your sketch show well the columnar habit (=crystal shape) and two cleavage planes at 90° to each other.
Specimen 5. Potassium feldspar (variety: microcline)
Chemical formula:
Sketch:
Scale x______
Try to illustrate two cleavage planes at 90° to each other.
Specimen 6. Quartz
Chemical formula:
Sketch:
Scale x______
Identify on your sketch at least two crystal faces and an area of conchoidal fracture.
Specimen 7. Thin section or saw-cut chondritic meteorite (please do not touch samples).
Sketch:
Scale x______
Be careful with your scale, and denote chondrules and matrix.
Specimen 8. Iron meteorite (please do not touch sample)
Sketch:
Scale x______
Label the Widmanstatten pattern (caused by slow migration of Ni out of darker bands, leaving Ni-poor alloy—diagnostic of meteoritic origin because it takes millions of years to form).
Check out the two rocks at the front. Which two minerals make up the larger one?
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Lab 1, Ge 101, Fall 2013/Page 1