Tuttle

Here is another example of an igneous rock. This one has a darker red color, and that’s because it is dominantly composed of a pink mineral called feldspar. In fact, all of the igneous rocks in Parsons are composed of some combination of eight basic types of minerals known as the rock-forming minerals. (Image 2)

Although there are over 4,000 unique minerals found around the world, there are only a few that are very common, including the eight rock-forming minerals. The overall color an igneous rock displays is a direct reflection of which of these minerals the rock is made of. It’s important to note that some of the minerals above come in a range of colors. For example, Feldspar is typically pink, but it can also be white. Anorthite can be light to dark grey in color, while Albite can be white to light grey in color. Quartz comes in a range of colors including milky white, grey, orange, pink and it can also be colorless and transparent. You will see examples of all these minerals except for olivine and muscovite. Rocks which have a lot of those two minerals in them don’t make good markers because the rocks are susceptible to weathering. (Image 3)

Although the rocks at Stops 1 and 2 are made of the same types of minerals, the rock at Stop 1 has more white quartz than the rock Stop 2, so its overall color is lighter. In general, igneous rocks fall in one of four categories in terms of their composition: felsic, intermediate, mafic or ultramafic. Ultramafic rocks are rare, and not used as cemetery markers, so we won’t discuss them further. (Image 4)

Before we move on to the next stop, take a moment to look at the top of the Tuttle marker. Unlike the sides, the top has not been cut and polished. As a result, it looks a lot different, and it is harder to pick out the individual minerals. When you polish a rock, the individual minerals become much more prominent, and the colors are more vibrant. (Image 5)