Official Stuff
This cache is hidden in Sells Mill Park, with permission of the Jackson County Manager. Please observe all park rules. At the time of publication, the park is open daily from 8 AM to 10 PM (Note: hours may change). There is parking nearby.
This Cache
Welcome to Sells Mill Park! I've been to this park several times, hunting geocaches, attending events and CITO's. It's a beautiful location!
One day, while visiting the park, the sun was shining and I couldn't help but notice the rocks here absolutley glistening. All I could think, was "WHY IS IT SO SPARKLY!?!?!?!?!" ✨ Upon further examination, I noticed some interesting features. So, I decided to create an Earthcache so that others could see this area and learn a bit about the features!
This is an Earthcache. That means there is NO PHYSICAL CONTAINER! To be able to log a find for this cache, you must examine the "sparkly" rocks (there are plenty of them near the top of the hill) and complete these tasks/answer these questions:
Task 1: Include a photo 📷 of yourself, or a piece of paper with your geonick as part of your log. Note that the photo is a requirement, and logs without a photo will be deleted! 😱
Task 2: Do you see any Foliation in the sparkly rocks here (Definition below)? Describe what you see.
Task 3: Based on the description below, what makes the rocks sparkly? Is the sparkly stuff particularly valuable? Is it rare? Give an example of something it can be used for?
Task 4: When you rub your hand/finger on the sparkly rocks, do the "sparkles" separate easily from the rock? Or are they firmly embedded in the rock? (i.e. did you get any "sparkles" on your hands??). Based on the information below, why is it that way?
Task 5: Based on the information below, would you say the rocks here are Granite, Pegmatite, or Schist? Justify your answer.
Task 6: One of the reasons you can see the rocks so clearly here is the erosion of the area. Looking around you, what do you think is the main driver in creating this "valley" you are standing on the edge of?
Please send your answers through the geocaching messaging app. If you are visiting the site with multiple people, it is fine for one person to send the answers, but please make sure you list the people in your party. Note that if multiple people are visiting at the same time, each person must submit a picture 📷. Logs without the required answers or photo may be deleted.
Note: more information about what you see follows below...
Thanks for visiting my Earthcache!
WHY IS IT SO SPARKLY!?!??!!
The rocks you are looking at here are loaded with a material called MICA. This is what makes them sparkly!
Mica is geologically widely distributed and occurs in igneous, metamorphic and sedimentary rocks. It is particularly prominent in many:
- Granites: Granite is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. Granite is nearly always massive (lacking any internal structures), hard, and tough.
- Pegamites:Pegmatites are exceptionally coarse-grained igneous rocks composed of interlocking crystals, with individual crystals usually over 1 centimeter (0.4 in) in size and sometimes exceeding 1 meter (3 ft). As these rocks are forming, the materials are typically very fluid, allowing minerals within the rock to pool together. This means that pegamites often contain very large crystals.
- Schists: Geologists define a schist as medium-grained metamorphic rock that shows well-developed schistosity (Schistosity is a thin layering of the rock produced by metamorphism that permits the rock to easily be split into flakes or slabs). The word schist is derived ultimately from the Greek word schízein, meaning "to split" which refers to the ease with which schists can be split along the plane in which the platy minerals lie.
Micas are translucent to opaque with a distinct vitreous or pearly luster, and different mica minerals display colors ranging from white to green or red to black. Deposits of mica tend to have a flaky or platy appearance.
Often called 'white mica', muscovite is the lightest colored mica mineral.. Muscovite is particularly common in metamorphic gneisses, schists, and phyllites. Muscovite often occurs as microscopic grains that give these rocks their silky or shiny appearance. Micas are characterized by a crystal structure consisting of weakly bound aluminum silicate sheets. This weak bonding makes it fairly easy to separate the mica from its host rock.
Foliation
While you might mistake the layering you see for a sedimentary deposit, what you are seeing is called Foliation. Foliation is a rock characteristic that looks like fine layering in the rock. These layers form during metamorphism and often make the rock look like it might break into thin sheets. The foliation forms due to minerals being squished and flattened by the intense pressure that exists during metamorphism. The presence of foliation will tell a geologist that this rock experienced the intense heats and pressures required to cause the minerals to squish and rotate in this way. The only natural forces known that can cause foliation like this are continental collisions.(The foliation here is the result of the African and North American continents colliding!) 😱
How We Use Mica
Small pieces of mica like you see here can be used in a number of applications. In larger deposits, the mica can be extracted in "sheets" which serves a number of purposes. The largest documented single crystal of mica was found in Lacey Mine, Ontario, Canada. It measured 33 ft × 14 ft × 14 ft and weighed about 330 tons!!!
The earliest use of mica has been found in cave paintings created during the Upper Paleolithic period (40,000 BC to 10,000 BC). The first hues were red (iron oxide, hematite, or red ochre) and black (manganese dioxide, pyrolusite), though black from juniper or pine carbons has also been discovered. White from kaolin or mica was used occasionally. Throughout the ages, fine powders of mica have been used for various purposes, including decorations.
Today, The leading use of dry-ground mica in the US is in the joint compound for filling and finishing seams and blemishes in gypsum wallboard (drywall). The mica acts as a filler and extender, provides a smooth consistency, improves the workability of the compound, and provides resistance to cracking. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension, reduces chalking, prevents shrinking and shearing of the paint film, increases the resistance of the paint film to water penetration and weathering and brightens the tone of colored pigments. drywall and paint applications accounted for approximately 75% of the dry-ground mica used in 2008!
Sheet mica is used principally in the electronic and electrical industries. Its usefulness in these applications is derived from its unique electrical and thermal properties and its mechanical properties, which allow it to be cut, punched, stamped, and machined to close tolerances. Specifically, mica is unusual in that it is a good electrical insulator at the same time as being a good thermal conductor.
Some other interesting uses for mica include:
- Thin transparent sheets of mica were used for peepholes in boilers, lanterns, stoves, and kerosene heaters because they were less likely to shatter than glass when exposed to extreme temperature gradients
- Sheet mica used as a window on radiation detectors such as Geiger–Müller tubes.
- Dry-ground mica is used in the production of rolled roofing and asphalt shingles
- Wet-ground mica, which retains the brilliance of its cleavage faces, is used primarily in pearlescent paints by the automotive industry.
- Mica is used in cosmetics and food[9] to add "shimmer" or "frost."
Mica is definitely some cool stuff!!!!