Since 2004, the official state gemstone for the state of Maryland is the Patuxent River Stone (pictured below). There are many reasons why it could be symbolic for Maryland. For one, fit the criteria of being "rare but findable, existing in sufficient quantity to allow for a reasonable source of supply for local artisans." For another, the brilliant yellow and red hues match those in our beloved state flag. Lastly, it is only found in Maryland, in a narrow formation called the Arundel Formation which stretches along the I-95 corridor between DC and Baltimore.
This EarthCache will take you to a gravel bar in the Middle Patuxent River. A bar is an elevated region of sediment in a river that has been deposited by the flow of the river, and you can tell that many of these rocks have been deposited here by the river since they are so smooth. This might be a prime spot to discover a Patuxent River stone! If nothing else, we bring you here as it's the best place our boys have found to skip and throw rocks into the water in a year-plus of geocaching. When you get to GZ, take a close look at what you're standing on - you might find one!
Amusingly, the Patuxent River Stone has come under criticism. Some gem and mineral enthusiasts have argued that it is not agate or fossilized dinosaur bone after all, as the state claims, but instead a form of quartzite. Quartzite is a hard metamorphic rock which was originally quartz sandstone. Sandstone is converted to quartzite through intense heat and pressure, which recrystalizes the individual sand grains into an interlocking mosaic of quartz crystals. Thus, the grainy sandpaper-like surface of the rock will become glassy and smooth. The brilliant red inclusions are due to the presence of iron oxide (rust), and the inclusion of other minerals can cause the quartzite to be yellow, blue, green, or other colors. Quartzite is very common in many parts of the U.S., including the Washington DC area, and is often cut for use as kitchen countertops.
A map of the Arundel Formation from a journal article (note how Baltimore is in the wrong place.)
Citation for image: Frederickson, J. A., Lipka, T. R., & Cifelli, R. L. (2018). Faunal composition and paleoenvironment of the Arundel Clay (Potomac Formation; Early Cretaceous), Maryland, USA. Palaeontologica Electronica, 21, 1-24.
To log this cache (required):
Please post a picture from the site. It could be of you, a personal item, or any potential Patuxent River stone that you might find.
In addition, please email me with the answers to the following questions:
1) Why is the Patuxent River stone called the "most embarrassing state gemstone"?
2) How was it formed?
3) What causes the red colors in the stone?
4) What is a bar in this context?
To find this EarthCache, there are several walking trails down from the neighoborhood on the north side. The easiest route is probably to drive south on Eden Brook Rd. until it is closed off. If you park there, you can walk down to the river on what is basically a road with no cars on it. As you get close to the gate near the river, there is a path on your right which will take you upstream. When you reach the orange petroleum pipeline bars, there is an entry down to the gravel bar on the river.