This weeks class was very interesting  because we got to do our first lab, finally.  After three weeks of nothing but powerpoints, notes, and readings, we finally got to do something with a hands-on approach to it.  We got to explore different types of minerals by identifying different qualities of each one.  We first looked at the hardness of each mineral, which is a measure of the resistance to abrasion or scratching.  I found that by comparing each mineral to common day items such as glass, iron nails, or other minerals, that you could tell the tested mineral’s hardness.  The trick was to scratch one item against the other to see which one was scratched.  Then in turn, we could figure out which had a higher hardness rating, which we also learned was on a scale of 1 – 10.  Something I learned from this portion of the lab was that my fingernail is a 2 on the scale, and a copper penny isn’t much higher at as little as a 3.5. 

The second test we put the minerals through to try to identify them was a color and streak test.  This was very basic and nearly effortless to do.  For color you basically just look at the mineral and record that general color in apperance.  For streak, we used a streak plate (unglazed ceramic white or black plates) to rub the mineral at hand against it and see what color the mark it left was on the plate.  The color and streak test turned out to be one of the least helpful identifying methods for the minerals because specimens such as quartz could be many different colors.  We learned in class this week that if a mineral has a small amout of any element, such as iron, it will change the color almost completely. 

The third test was similar to the color test as we determined the mineral’s luster by observing its apperance.  We could tell the elements luster by identifying it as shiny, glassy, resinous, pearly, silky, etc.  Some of the minerals were a little bit more difficult to gather a recording for its luster than others. 

The fourth method we used was cleavage and fracture.  This method of identification was the hardest of the five to record.  A mineral is said to have “cleavage” if it breaks into even planes, or into identifiable angles.  Fracture occurs when there is no specific order in the way the mineral breaks.

The last method we use was finding the tenacity of the minerals.  These classes include brittle, sectile, malleable, flexible, and elastic.  Prior to this class I know what the last three meant, but I learned that brittle meant it would shatter if struck by a hammer, and that sectile meant it could be cut with a knife or scissores and not break into grains. 

Something I recently read about that related to geology was from science daily . com.  A group of researchers is working on creating a complete seismic image of the subduction zone beneath the Himalayan Mountain range.  The article wasn’t particularly long or detailed but I still think it is interesting that scientists are trying to figure out how the earth is working.

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One Response to

  1. Jessica Tibbs says:

    I had the hardest time trying to figure out what the cleavage was. I still do not totally understand the concept, but i am trying. So I agree that it is the hardest technique to use to identify a rock.

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