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.
Here, you will explore the fascinating world of mica minerals, which are a significant part of many rocks and soils. The samples of Mica located at GZ have been carefully curated into the Burford Warm Memorial and surrounding stone wall. The War Memorrial is open from dawn until dusk, 7 days per week. Please limit your visit to daylight hours for this reason.
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.
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 a large Cairn with many rocks. Many of these specimens have samples of mica contained within them. How will you know you're looking at Mica? Look for stones within the cairn and surrounding wall that have a reflective surface, and may appear smooth, sparkly or greasy. All of your observation will come from this cairn or the surrounding wall - I saw more than 20 samples to choose from when selecting wwhere to record your observations within 10m of GZ.
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 the cairn or wall? If so, describe which one(s) you see.
4) Estimate how much of the total cairn (not rock wall) is actually mica.
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 or near the posted coordinates with the War Memorial visible in the Background. You do not need to show your face if you are shy. 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.
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.