Brown Mausoleum
We start our geologic tour at the largest and most obvious mausoleum in the cemetery. Virtually all of the markers in Parsons Cemetery are made of rock. So, what is a rock? A rock is a naturally-occurring substance made up of one or more different minerals. One marker, which you will visit on this tour, is made of metal, and a few are made of concrete. Concrete is not a real rock. (Image 1)So, what is a mineral? A mineral is a naturallyoccurring inorganic solid that possesses a definite chemical structure (also known as a crystal lattice), giving it a unique set of properties. One of the most obvious properties is color, and you will see minerals of all sorts of different colors on this tour. If you look closely at the rock which the Brown mausoleum is made of, you will see it has several different distinct types of minerals. Because most of the minerals are pink to red in color, the overall appearance of this rock is pinkish-red. (Image 2)So how do rocks form? Well, that depends on the type of rock. Most of the rocks which make up the Earth’s crust are formed by the cooling of molten rock called magma or lava. When the molten rock is found inside the Earth, it’s called magma, but when the molten rock flows out on the Earth’s surface during an eruption, it’s called lava. In either case, the molten rock will cool, and minerals will form through a process called crystallization. That’s how the rock at Stop 1 formed. These types of rocks are called igneous rocks, and many of the markers in Parsons are made of igneous rocks. (Image 3)
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)
Adkins
Although the red and pink markers are very pretty, you will find that most of the markers in Parsons are grey, like this one here. The key difference is the absence of the pink feldspar minerals. This rock is made exclusively of white, grey and black minerals. This rock would be classified as felsic. (Image 2)Most of the “igneous” markers in Parsons are one of the six types of igneous rock shown above. The terms geologists use to classify different types of igneous rocks are based on the relative proportion of the different minerals they contain. For example, granite or granodiorite will have a large amount of quartz, syenite or monzonite will have very little quartz, and diorite or gabbro will have no quartz at all. (Image 3)The marker at Stop 1 would be classified as a granite, the marker at Stop 2 would be classified as a syenite, and the marker at Stop 3 is a granodiorite.
Leona E. Adkins
This rock would be called a monzonite, which has a darker gray color than the marker at Stop 3. But there is another key difference between this marker and the previous one. They have different sized crystals. Some igneous rocks have bigger crystals than others. (Image 2)How big the crystals grow in an igneous rock is a function of how fast the magma cools. If the magma cools quickly, the crystals will be small in size. If the magma cools slowly, the crystals will be large in size.Geologists use different terms to describe the general size of the crystals in an igneous rock. Aphanitic rocks have very small crystals, so small that they are not visible to the naked eye (although you might pick out one occasionally). Aphanitic rocks are not commonly used as cemetery markers because they aren’t very durable. Most of the igneous rocks in Parsons Cemetery are phaneritic, meaning the crystals can be seen with the naked eye. Pegmatitic rocks have crystals which are larger than a dime. Porphyritic rocks have two groups of distinctly different-sized crystals. (Image 3).
Kelley
This rock is also phaneritic in texture, but the crystals are smaller than at Stop 4. It is also a granodiorite based on its composition.
Robertson
This rock is a granite, but it is also a good example of a pegmatitic igneous rock. The pink feldspar crystals in this marker are quite large in size. The black minerals are called hornblende.
Sirman
This rock is an excellent example of a rock with a porphyritic texture, one of the only ones in Parsons. It has very large albite crystals, while the other minerals are considerably smaller. This rock would be called a porphyritic monzonite.
Smith
This rock has very small crystals and would be called a granodiorite. It is one of the lightestcolored markers in the cemetery. It also has not been polished.
Purnell
Now for something new. In contrast to the lighter-colored igneous rocks you have seen so far, this one is very dark in color. This is a good example of a gabbro. If you look closely, you can see the individual crystals, which means it is phaneritic too. When it is polished, it looks black, but it is actually composed of predominantly dark grey anorthite minerals along with black hornblende minerals.
Parker
This marker has small crystals and is called a diorite. You can see it has a mixture of dark hornblende minerals and light albite minerals.
Toadvin
This marker would also be called a diorite and it is similar in composition to the rock at Stop 10. In this case, there are more white minerals (albite) and less darker minerals (hornblende and anorthite), which gives it an overall lighter color than the marker at Stop 10.
Brenizer
Here we have a marker which is very different from anything you’ve already seen on the tour to this point. This is a new type of rock called a metamorphic rock. Metamorphic rocks are commonly used for cemetery markers as well as kitchen countertops and floor tiles. This marker is made from a rock called gneiss (pronounced “nice”). (Image 2)To understand how a metamorphic rock forms, we need to discuss the rock cycle. The rock cycle explains how different types of rocks form and change over time. When rocks are exposed at the Earth’s surface, they are broken down into sediments by the process of weathering. These sediments are commonly carried away by the process of erosion and deposited somewhere else, usually in a body of water like the ocean. As these layers of sediment pile up, they become cemented together through the process of lithification, forming a sedimentary rock. (Image 3)Most sedimentary rocks are generally not suitable for use as grave markers, either because they are weak or hard to carve cleanly. However, if a rock gets buried deep in the Earth, it can undergo a transformation called metamorphism. Metamorphism takes one type of rock and slowly changes it into a new rock with different properties. Commonly, these new metamorphic rocks are both denser and stronger than the original rock. This makes metamorphic rocks suitable for cemetery monuments. Although they aren’t common in Parsons, some of the prettiest markers are made of gneiss, which you will see later in the tour.
Booth
This marker is a diorite, and it is similar to the rocks at stops 10 and 11. What makes this marker different are the long, slender white minerals, which give the rock a different look.
Ball
This marker is another good example of a monzonite. Many of the dark grey markers in Parsons are monzonites.
Booth
This is one of the most unusual markers in Parsons. It is not made of stone, but instead, it is made of zinc. The pieces would have been formed in a mold and then welded together. They are cheaper than monuments made of stone, and resistant to algae and moss growth.
Jackson
This marker is made a metamorphic rock called marble. Many of the markers in Parsons, especially the older markers, are made of marble. Marble is made of a mineral called calcite. Calcite is the same mineral that clams and snails use to make their shells.
Taylor
Being able to tell the difference between a marble and an igneous rock like granite can be challenging. Lucky for us, we have examples of each sitting side-by-side at Stop 18. The marker on the left is made of pink marble, while the marker on the right is made of pink granite. They are both made of crystals of about the same size. The key difference is that the granite is made of several different types of minerals, whereas the marble is only made of calcite. The dark streaks are caused by impurities in the rock. Many marbles have these dark streaks running through them.
Bozman
This is another example of a marble. This marble also has the dark streaks running through it. Marble starts out its life as a sedimentary rock called limestone. Limestone, which is also made of calcite crystals, commonly forms in warm, shallow tropical seas. There is a large marble quarry north of Baltimore which is still active today. If you look at this marker closely, you can see the individual calcite crystals. They are smaller than the crystals in the pink marble at Stop 17. You can also feel them if you run your hand across the marker face.
Goslee-Mitchell
Although marble is a very attractive stone which can be easily carved into different shaped markers, it has one major problem. Calcite is a mineral which readily dissolves in the presence of acidic water. Unfortunately, rainwater is slightly acidic. As a result, many of the older markers in the cemetery are becoming hard to read as the marble dissolves away. Eventually they will be completely unreadable. For this reason, marble is not commonly used for markers anymore. In the 19th and early 20th century, marble was commonly used because it was a cheaper. But igneous rocks are much more durable, and they are not as expensive as they used to be, so now igneous rocks are mostly used for markers in Parsons.
Kennerly
That doesn’t mean igneous rocks aren’t susceptible to weathering over time. The marker at this stop is made of granodiorite, but you can see the weathering process has stained it and moss is growing on it. Mosses and lichens can break rocks down over time. Still, igneous rocks weather much more slowly than marbles
Benedict
Now that we’ve discussed the basic principles of rocks, and discussed which types are used for markers, we’re going to explore some more examples of markers in Parsons. This pretty crypt is made of granite.
Chatham
At first, this marker may look like it is an igneous rock, but in fact this is another example of a gneiss. You can tell it is a gneiss because the minerals are lined up in large bands. In general, if you see a rock which is made of different colored minerals which appear as large, flowing bands, it is most likely a gneiss.
Kane
This marker is a one-of-a-kind in Parsons. The blueish color is from a mineral called labradorite. Labradorite is a mineral which has a pretty, iridescent blue color when viewed from the right angle. This is what gives this igneous rock its blueish hue. Although it is not very dark in color, this rock is a type of gabbro. On a sunny day, if you find the right angle, you should be able to see the blue “pop” out.
Bailey Mausoleum
This mausoleum is made of granite, but it has a unique feature that makes it different from the other granite markers in Parsons. To see what I mean, look at the west-facing side of the mausoleum and look for the large dark mass as shown above. This large, dark mass is called a xenolith (pronounced “zee-no-lith”). There are several dark xenoliths of different sizes in this slab of granite, but this is the largest. (Image 2)Xenoliths form when magma rises up from the Earth’s interior and pushes its way into the rocks in the Earth’s crust. Sometimes, pieces of the “country rock” fall into the magma. The pieces of rock don’t necessarily melt, but instead, they get incorporated into the newly forming igneous rock. In this case, there are xenoliths of diorite within the granite. (Image 3)
Nelson
This is another example of a gneiss. You can tell it is a gneiss because the minerals are lined up in bands.
May
Although this marker isn’t the most colorful, it has a most unusual feature. Just like at Stop 24, this marker also has labradorite minerals in it. As it so happens, one crystal is orientated in just the right way such that the bright blue iridescent labradorite “pops” out prominently. There are several markers in this part of Parsons which are made of this type of rock (monzonite), but this is the only marker with this feature.
Kiley
This is a good example of a granite, and this particular granite has a light pink color which is not common in Parsons.
Smith
This is another example of a gabbro. This gabbro is unusual because it is made of flat, slender crystals of dark grey anorthite. There are also some black-colored crystals of hornblende.
Goodge
We have arrived at the final stop on this tour. This is yet another example of a gabbro. This gabbro is unusual because it has a mixture of different shaped crystals. There is no other marker like this in Parsons.
The End
We hope you have enjoyed this geologic tour and that you have gained a deeper appreciation for the markers in Parsons Cemetery and the variety of rocks they are made of. Below is a summary of the concepts we covered on this tour:What is a rock?What is a mineral?What are igneous rocks?How do igneous rocks form?What are the common minerals that igneous rocks are made of?What are the names of the igneous rocks used for markers in Parsons?What are the different types of igneous rock textures?What is the rock cycle?What are metamorphic rocks?What is marble and how does it form?What is a xenolith?All of the images and diagrams in this tour were created by Brent Zaprowski unless otherwise noted.
