Getting the Rocks Ready in the Lab

Trip Start Jan 30, 2007
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Trip End Aug 08, 2007


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Flag of United States  , California
Saturday, January 13, 2007

Jonathan, my husband (it is acutally his research sabbatical and I get to help him!!) is working hard to get his samples ready for making thin sections, which is what you call microscope slides that have a very thin layer of rock on them. You can actually take a rock, stick it to a glass slide, and then grind it down to a very thin layer. The layer gets thin enough to see through. You can then put the thin sections under a special microscope that geologists use called a petrographic microscope. Looking at a slide, you can see what minerals a rock is made of and what sort of history the rock might have had (for example, you might see if the rock has been slightly metamorphosed or whether mineral-rich fluids might have altered it, etc.). You can also put in these filters on the microscope and it turns some of the minerals bright colors, which also helps in identification.

Jonathan also needs to grind up the rock samples for some of the geochronology analysis work (analysis to figure out how old the rock is) that he will be doing. He only needs certain minerals in the rock. The first part of getting to these minerals is to crush th rocks down into tiny pieces. From looking at the pictures, you can see that he is crushing very fresh (so fresh that it is very clear) obsidian, which is volcanic glass, from the Coso Geothermal Field down by China Lake in Southern California.

After crushing the rocks, Jonathan and one of his students, Jamie, put the rocks on the Wilfley Table. This table vibrates and has water running over it. The heavy minerals that Jonathan needs for analyzing get separated mostly by density and can be collected.
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