 In this lesson we learned about garnet. Personally, garnet is one of my favorite minerals. Garnet is beautiful. I have some garnet jewelry on today. It is also functional. Garnet has a lot of industrial and household uses as an abrasive, it's used in sandpaper, it's used for polishing, and it's used in sand blasters and water jet cutters. Garnet is also really, really useful scientifically for geoscientists who are interested in understanding what has happened in Earth history in terms of the plate tectonics and moving plates, building of mountains. Garnet serves as an index mineral which lets us know what the metamorphic grade was. That was achieved in a particular mountain belt or in a particular metamorphic setting. Garnets can be dated, so we can get ages and not only that, but garnets grow concentrically starting at a seed and growing outward like tree rings. So we can get multiple dates from one garnet that has grown over the course of perhaps as many as millions of years. And then within that time range, we can use garnet and inclusions of other minerals that get trapped inside of the garnet as it grows form some calculations that we can make that are useful as thermometers and barometers, so what we call a geothermometer or a geobarometer that allow us to calculate based on the composition of the garnet and the composition of the other minerals that we find inside of it exactly what pressure and temperature the garnet has experienced. And what that means is by looking at one garnet that grew over a long period of time, we can calculate, we can determine exactly how the pressure and temperature changes that were experienced by that garnet, how they changed through time and map out the history of tectonic events, something like a mountain building or a subduction zone carrying ocean crust deep into the interior of the earth and understand the rates of how these processes happened and when in time they've happened. So I think it's pretty cool. So another very cool thing about garnets is that they can also inform us about somewhat more recent history and it's because garnets can be proven quite accurately thanks to a lot of the properties that Maureen was just describing. And so as you learned in the video from the Römisch-Germanisch Zentralmuseum in Mainz, there was a project in Germany to provenance a bunch of garnets that were used in Frankish and Anglo-Saxon and other types of Germanic jewelry from sort of the migration period in Europe. So roughly between about 400 and seven or 800 CE. And with those they found that most of them were coming from particular areas of Rajasthan and from Sri Lanka but that there was also a change in the trade routes that must have occurred right around 650, 700 because we start seeing changes in the garnets themselves and the types of garnets. There's more evidence of reuse in some of the later, the more recently made pieces of jewelry. And garnet can be used as a substitute to sort of inform historians and particularly historians of economics about trade routes for other materials that we don't have surviving examples anymore. So for example, the spice trade or trade in textiles where we might have some material remaining but it tends to be much more fragmentary. And so garnets are a wonderful stand in for economic historians and art historians in order to examine those trade routes. And again, they're beautiful and highly symbolic when we're talking about the red ones.