 Now we're going to talk about the mineral property of hardness, and it's a little bit more of a complex test to perform. And it can be complex because it can be done in a couple of different ways. So we have a set of reference samples where we know their hardness, and then we've got the sample minerals that we're going to try to compare to the reference materials. Now just theoretically speaking, if I have a glass slide, if a mineral is softer than glass, it can't scratch the glass. If a mineral is harder than glass, it would scratch the glass. In this particular simulation, they actually do it the other way around. They see if the glass can scratch the material. If the glass can scratch the material, the material must be softer than glass. Or if the glass can't scratch the mineral sample, then the mineral sample must be harder than glass. Again, in a laboratory, you can do the testing in both directions to figure out which one is harder and which one is softer, comparing mineral samples with a variety of reference samples. Now here in this simulation, we have it set up so that you can use the reference samples to try to scratch the sample minerals. So for example, I could pick up a fingernail and see if I can scratch it. Now it will always make a scratching sound. To let you know whether or not you were able to do that test. But that doesn't tell you whether the mineral was actually scratched. Now you might be able to tell with some magnifying glasses looking at the particular samples to see if you see scratch marks. But again, the video is not so clear. But it does have another way to know for sure. I'm going to start by picking up the diamond and diamond is an incredibly hard material. So we should expect that the diamond could scratch any one of the materials. Now again, if I look at it, I can kind of see the scratch marks. But the easier way to tell is if I pick up a different reference sample, if it was scratched, it comes in and turns the piece over. So let me show you to that again. I took the diamond, I scratched it. Then when I go to pick it up, when I move this over the mica, you're going to see a second hand come over and flip the mica over. That lets you know that the mica was really scratched and they're giving you a fresh clean surface to do your next test. Now that I've gone through and explained how the test works, I'm going to make a separate video that just has the actual experiments in it. And I'm going to take these particular samples and I'm going to use the ones that are in the lab report and test them on these minerals so that you'll be able to mark off on your chart which ones did or did not scratch the material.