What’s so Shiny?

Please see the coordinates for the trailheads and trail intersections below. Both hiking and bicycling are allowed on these trails.

Option 1: From the County 3A trailhead take the Made in the Shade trail. It is a loop and you can go either direction but counter clockwise is the shortest way to the cache. At the trail intersection coordinates turn onto the One Track Mind trail which will take you to the cache. This option is about 5 miles round trip.

Option 2: From the Point Alta Vista trailhead use the Point Alta Vista trail for about 1 mile. At the intersection the One Track Mind trail will go NE over some bare rocks then make a hard right turn to the south just after entering the trees. This is about 6 miles round trip.

Please stay on the trails. There is a lot of surrounding private property especially when using the Point Alta Vista Trailhead. Be respectful and do not go on private land. The Canon City region of Trailforks.com has an excellent map of the trails.

What is mica?

Micas are a group of phyllosilicate minerals. The distinguishing characteristic of mica is that the crystals form in such a way that it can be easily split into very thin sheets. All micas have a similar crystal structure but vary greatly in chemical composition. Those variations mean that some are nearly see through and others allow no light through. They also create a wide range of colors including white, green, red and black. Most of them have a shiny, glassy appearance.

Mica is found all over the world and in all three major types of rock: igneous, metamorphic and sedimentary. When it is present in sedimentary rock it is usually only very small flakes but the crystals can be quite large in other types. Individual mica crystals that are several feet across have been found and those are usually in a type of igneous rock call pegmatite. Large crystals of mica are referred to as “books” since the edges look like the pages of a book. Figure 1 shows “books” of mica in a rock near GZ. (This is not the book you need to find for your answers).

There are many industrial uses for mica. It’s ground up for some and used in sheets for others. One of the most common uses of ground mica is for joint compound that is used to fill and finish seams in drywall. It’s also used in paint to increase its resistance to water and weathering as well as brightening the color. Many cosmetics get their sparkle from ground mica. You might even find ground white mica in your toothpaste where it acts as a mild abrasive. Mica is essential to the electronics industry because it is a good electrical insulator and also can be cut and machined to close tolerances. Its transparency combined with its resistance to heat make it ideal for certain laser devices and industrial blast furnace windows.

The most common form of mica is muscovite. It can vary from colorless to tints of grey, brown, green or yellow. It can be totally transparent or translucent meaning it isn't see though but does allow light through. The name comes from its use as an alternative to glass in medieval Russia (Muscovy). Figure 2 is an example of Muscovite.

The next most common form is biotite and is sometimes referred to as black mica. Iron and magnesium give biotite its dark black or brown color. It can also have green or white streaks. It is found in the same types of rock as muscovite and they can be found side by side. Figure 3 is an example of biotite.

To claim this Earthcache please send an email or message with the answers to the following questions:

1. At GZ you will see a rock wall next to the trail that measures about 8 x 10 feet. What percentage of the mica in the wall is biotite?

2. About 40 feet NNW of GZ (Stage 2 coordinates) there is a smaller rock wall. In that wall at about 18 inches off the ground you will find a “book” of mica facing upwards. What are the length and width of the book?

3. Look around the general area at the loose pieces of mica. How big is the largest piece you see? Is that piece muscovite or biotite?

Photos that don’t give away the answers are optional but highly encouraged.

Permission for this Earthcache was granted by Royal Gorge Park administered by Canon City, Parks Dept

References:

https://en.wikipedia.org/wiki/Mica#Early_history

https://en.wikipedia.org/wiki/Muscovite

https://en.wikipedia.org/wiki/Biotite

https://uwaterloo.ca/earth-sciences-museum/resources/detailed-rocks-and-minerals-articles/micas

Additional Waypoints

019PEHW - Stage 2
N 38° 28.453 W 105° 19.489
Smaller rock wall 40 feet NNW of GZ
R09PEHW - County Road 3A trail intersection
N 38° 28.357 W 105° 19.162
Intersection of Made in the Shade and One Track Mind trails
R19PEHW - Point Alta Vista trail intersection
N 38° 28.280 W 105° 20.204
Intersection of Point Alta Vista trail and One Track Mind trails
T09PEHW - County Road 3A Trailhead
N 38° 28.402 W 105° 18.467
Start and end of Made in The Shade trail
T19PEHW - Point Alta Vista Trailhead
N 38° 28.690 W 105° 19.728
Start of Point Alta Vista trail