M: Want to go out and get something to eat?
W: I can't.I have a chemistry midterm on Monday and a German exam on Tuesday.
M: I have a geology exam Monday myself,but I think I'm ready for it.
W: What kind of exam is it going to be multiple choice or essay?
M: Neither.The professor is going to give us a mineral sample and we have to identify it.
W: How do you do that? I mean,a rock's a rock,isn't it?
M: Actually,there are a lot of tests you can perform on minerals to help you figure out what they are.Probably the first tests I'll do are scratch tests.(1)_______________________.That tells you the relative hardness of the sample.
W: What other tests will you do?
M: I'll probably do a streak test next.In that test,you rub an unknown mineral against a piece of china to see what color the streak is.
W: Why can't you just look at the mineral to see what color it is?
M: (2)_______________________.But a streak test shows the mineral's true color. Then there's always the specific gravity test,the blowpipe test...oh,and...
W: And after you've done all these tests,can you positively identify any mineral?
M: Well, usually...but not always.I just hope I can on Monday!
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作者: longyuan 时间: 2013-5-22 08:00
1\When you do a scratch test you rub the sample on a know mineral to see if the unknow mineral scratchs the know mineral or vice visa.
2\Well you can but sometimes mineral has some other substance and the substance could change color.
