It's So Sparkly!
An Introduction to Mica & It's Uses
Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find. The goal of this Earth Cache is to educate visitors about the diversity of mica minerals, their properties, and their significance in geology and their many uses in the modern world. At GZ, you will find mica in it's natural form, within the many rocks exposed along the edge of the trail.
This earthcache does involve a short hike along the Little Ridge Trail, of approximately half a mile from parking (round trip). It is a relatively flat trail, with some tripping hazards such as exposed rocks (like the ones you will be examining for this eathcache) as well as tree roots. This is a popular trail for hiking, running, and walking. Dogs are welcome and may be off-leash in some areas of the park. As you wander along the trail, you will see some pink and grey rocks that contain mica, which is where you will begin your observations. Mica minerals are a significant part of many rocks and soils. The samples of Mica located at GZ are in their natural state, left in place from the last ice age. The park is open from 8am until 10pm, 7 days per week, however due to the visual nature of Earthcaches and the observations you are required to make, please limit your visit to daylight hours only.
EARTHCACHE REQUIREMENTS
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name. There is no need to send individual answers. Each cacher should include their own photo on their log.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
Observational Task
At GZ, you find exposed rocks with many shiny "bits" that seem to glisten in the daylight - this is the mica you are looking for. Many of the rocks along the trail have samples of mica contained within them - the posted waypoint is just one such example where I was able to easily make observations, however there may be others. If you decide to use a different sample to answer the questions, other than the one provided, please provide the coordinates of the location of your sample. It should be within Little Ridge Park.
How will you know you're looking at Mica? Look for stones along the trail that have a reflective surface, and may appear smooth, sparkly or greasy.
Questions to be Answered:
1) Based on the descriptions below, what type of mica do you think is most prevalent at this location and why?
2) Based on the description below, why do you believe this is mica and not some other type of sparkley mineral?
3) Is there more than one type of mica present within rocks at or near GZ? If so, describe which one(s) you see.
4) Estimate how much of the total rock at GZ is actually mica. Having a look around the area (within 40-50 feet) do you think there is more mica present that what we can see esposed along the trail?
5) Using only your finger nail, how easily does the mica flake off? Describe the appearance of the flake?
6) MANDATORY - Post a photo of yourself, your signature item, your GPS, at the posted coordinates with the rocks containing mica visible in the photo. You do not need to show your face if you are shy. A sample photo is included below, so you know what you are looking for. You may include this photo in your log, or send it with your answers but it must be provided as proof that you visited the area.
Update on Feb 23, 2025 - it appears that some cachers are not observing the correct rocks with Mica included at GZ, and are instead either making up their answers entirely or looking for the wrong thing.
The rocks you are looking for are part of the trail that leads right to the year 2000 cache from parking, and may be covered with mud, leaves and other debris. I am attaching a photo of my feet, at GZ, with these rocks, so you know specifically what you are looking for.
Moving forward, any logs that mention they did not find the rocks containing mica and trying to submit answers anyways will be deleted. Difficulty has been increased as a result.
EARTHCACHE INFORMATION
Types of Mica
Mica minerals are known for their sheet-like structure and are commonly found in igneous, metamorphic, and sedimentary rocks. Mica is commonly found in Canada, and Canada was once regarded as the leading producer of phlogopite mica in the world. In this Earth Cache, we will focus on the different types of mica: Muscovite, Biotite, and Lepidolite.
1) Muscovite
Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. It is characteristic of peraluminous rock, in which the content of aluminum is relatively high.
Appearance: Muscovite is usually colorless, pale green, or brown. It has a glassy to pearly luster.
Properties: Known for its perfect cleavage, allowing it to split into thin, flexible, transparent sheets.
Uses: Muscovite is used in electrical insulators and as a fireproofing material due to its high dielectric strength.
More Information: Sheets of muscovite have high heat and electrical insulating properties and are used in the manufacture of many electrical components. Muscovite sheets were used for kitchen oven windows before synthetic materials replaced them.
2. Biotite
Biotite is a sheet silicate; iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite).
Appearance: Typically black, dark brown, or dark green with a vitreous to pearly luster.
Properties: Like muscovite, biotite can be split into thin sheets. It is rich in iron and magnesium.
Uses: Biotite is mainly used for geological study to determine the thermal history of rocks.
3. Lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al) 3(Al,Si,Rb) 4O 10(F,OH) 2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
Appearance: Often pink, purple, or gray with a pearly luster.
Properties: Contains lithium and has a flaky structure similar to other micas.
Uses: Lepidolite is a source of lithium, which is used in batteries, ceramics, and glass production.
More Information: Lepidolite mica is one of the rarer forms of mica and is not commonly found in Canada. It is an ore of lithium and typically forms in granitic masses that contain high amounts of lithium.
Common Uses for Mica
The principal use of ground mica is in gypsum wallboard (drywall) joint compound, where it acts as a filler and extender, provides a smoother consistency, improves workability, and prevents cracking. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension. The ground mica also reduces checking and chalking, prevents shrinkage and provides increased resistance to water staining and weathering, and brightens the tone of colored pigments. Ground mica also is used in the well-drilling industry as an additive to drilling “muds" and in costmetics as a pigment, commonly found in eye shadows and blush.
The plastic industry used ground mica as an extender and filler and also as a reinforcing agent. The rubber industry uses ground mica as an inert filler and as a mold lubricant in the manufacture of molded rubber products, including tires.
Sheet mica is used principally in the electronic and electrical industries. The major uses of sheet and block mica are as electrical insulators in electronic equipment, thermal insulation, gauge “glass”, windows in stove and kerosene heaters, dielectrics in capacitors, decorative panels in lamps and windows, insulation in electric motors and generator armatures, field coil insulation, and magnet and commutator core insulation.
This earthcache has been placed by a Proud Platinum Earthcache Master.
