|Grade Level||Learning Style||Learning Cycle||Duration||Views|
|5, 6, 7, 8||Visual, Verbal, Kinesthetic, Interpersonal||Engage, Explore, Explain, Elaborate/Evaluate, Extend||45 Minutes||475|
Students will learn
- About the chemical characteristics of minerals
- Talc piece, for extracting powder
- 100-grit sandpaper, for getting fine talc powder
- 220-grit sandpaper, for very fine talc powder
- 600-grit sandpaper, for super fine talc powder
- No. 4 (0000) steel wool, for ultra fine talc powder
- Old blue jean rag or soft cloth, for glossing the surface of the talc piece
- Cut the talc piece on a wood band saw to obtain a flat surface to polish.
- Start with the 100-grit sandpaper; sand the flat surface until you have made a small pile of talcum or “baby powder.”
Note:Remember, it doesn’t smell like baby powder because no fragrance has been added.
- Feel how soft and smooth the powder is.
- With the 220-grit sandpaper, continue to sand the same flat surface taking out all the deep scratches.
- Notice that the powder is finer;
- Note: It is the same as that used in cosmetics (this is why we call it “Rocks on your Face”).
- Use the 600-grit black sand paper to produce an even finer powder.
- Note:Such fine powder is used in deodorants and in making paper, plastics, and paint.
- With the no. 4 (0000) steel wool take out the last of the scratches on the talc block and produce a very fine powder like that used on the outside of chewing gum.
Note:Remember, it is not powdered sugar but talc that keeps the gum from sticking to the wrapper
- With the old blue jean rag rub really hard to polish the talc surface by hand to a gloss.
Q1.Read the labels from a variety of cosmetic products. Is talc listed as one of the ingredients?
Q2.Discuss how talc is used in your daily lives.
Tips and Tricks:
- The process of finding or exploring for a mineral deposit, extracting or mining the resource, recovering the resource, also known as beneficiation, and reclaiming the land mined can be described as the “life cycle” of a mineral deposit.
- Mineral deposits are the source of many important commodities, such as copper and gold, used by our society, but it is important to realize that mineral deposits are a nonrenewable resource. Once mined, they are exhausted, and another source must be found. New mineral deposits are being continuously created by the Earth but may take millions of years to form.
- Mineral deposits differ from renewable resources, such as agricultural and timber products, which may be replenished within a few months to several years.
The technical definition of a mineral is a naturally occurring, inorganic, homogeneous solid with a definite chemical composition and an ordered atomic arrangement. In more general terms, a mineral is a substance that is:
(1) made of a single element like gold (Au) or a compound of elements like salt (NaCl) and/ or
(2) a building block of rock (for example, granite is composed primarily of the minerals quartz and feldspar).
- Minerals may be metallic, like gold, or nonmetallic, such as talc.
- Oil, natural gas, and coal are generally considered to be “energy minerals” and are not discussed in this report.
- A mineral deposit is a mineral occurrence of sufficient size and grade (concentration) to enable extraction under the most favorable conditions.
- Two cycles determine how mineral deposits are formed— the ROCK CYCLE and the TECTONIC CYCLE.
- Heat from the Earth’s interior melts some of the rocks in the crust (the upper part of the lithosphere).
- Molten rocks lower in density than the surrounding cooler material rise toward the Earth’s surface and eventually cool and harden near to or on the surface.
- The composition, temperature, pressure, and cooling process of the molten material determine the minerals and rock types formed.
- These are called IGNEOUS ROCKS and contain original or primary minerals.
- When these rocks are subjected to chemical and physical processes, such as freezing and thawing, they break apart into smaller fragments forming sediments.
- These smaller particles that compose the sediments can be physically transported and re-deposited by gravity, water, and wind.
- If the re-deposited particles are bound together by compaction or cementation (formation of new secondary minerals in the spaces between the loose particles), SEDIMENTARY ROCKS are formed.
- In regions where the Earth’s interior temperature and pressure are high enough to change the chemical composition and mineralogy of buried igneous or sedimentary rocks, without completely melting them, METAMORPHIC ROCKS are formed.
- Distinct groups or assemblages of minerals are typically associated with the formation of each of the three major rock types—igneous, sedimentary, and metamorphic rocks.
- PLATE TECTONICS play a major role in the processes of mineral and rock formation.
- In geologic terms, a plate is a large, “rigid” slab of solid rock.
- The word tectonics comes from the Greek root “to build.”
- The term plate tectonics refers to the process by which the Earth’s crust is formed and moved.
- The theory of plate tectonics states that the Earth’s outermost layer, the crust, is fragmented into a dozen or more plates of various sizes that are moving relative to one another as they are slowly transported on top of and by hotter, more mobile material (Kious and Tilling, 1996).
- Scientists now have a fairly good understanding of how the plates move and how earthquake activity relates to such movement.
- Most movement occurs along narrow zones between plates where the effects of tectonic forces are most evident.
There are four types of plate boundaries:
- Divergent boundaries—where new crust is generated as the plates pull away from each other.
- Convergent boundaries—where crust is destroyed as one plate dives under another.
- Transform boundaries—where crust is neither produced nor destroyed as the plates slide horizontally past each other.
- Plate boundary zones—broad belts in which boundaries are not well defined and the effects of plate interaction are unclear (Kious and Tilling, 1996).
- This activity is one of a set of activities designed to educate students about geology, plate tectonics, and mineral resources and how mineral resources are found, extracted, processed, and used.
- These activities are suited for the entire K-12 grade level range, but some may be best suited for the 5-8 or 9-12 grade levels (table 3). The activities are as follows:
Exploring for Minerals
Uses of Minerals
- Activity 6—Minerals in your Body
- Activity 7—The Mineral Talc or “Rocks on Your Face”– This current activity
- Activity 8—Make Your Own Toothpaste
- Activity 9—Mineral Flash Cards
- Activity 10—Personal Mineral Consumption
Mineral Resources and Economics
- Activity 4—Chocolate Chip Cookie Mining
- Activity 9—Mineral Flash Cards
- Activity 10—Personal Mineral Consumption
- Talc used in this activity should be a solid piece
Some information related to the Activity:
- Talc may have been the first mineral that most students came into close contact with.
- Talc is the main ingredient in talcum powder, which is used to prevent diaper rash.
Mineralogical characteristics of talc:
- Chemistry—Magnesium Silicate Hydroxide, Mg3Si4O10(OH)2
- Group—Clays (the Montmorillonite/Smectite Group)
Physical characteristics of talc:
Note: See Plante, Peck, and von Bargen, 2003 for an on-line description of the basic properties of minerals
- Color—green, gray and white to almost silver.
- Luster—dull to pearly or greasy.
- Hardness—1 (can leave mark on paper and be scratched with a fingernail).
- Specific Gravity—2.7 to 2.8 (average).
- Other Characteristics—cleavage flakes are slightly flexible but not elastic, and talc has a soapy feel to the touch (talc is sometimes called soapstone).
- Best Field Indicators—softness, color, soapy feel, luster, and cleavage.
For Evaluation and Discussion:
- Talc is an important industrial mineral.
- Its resistance to heat, electricity, and acids make it an ideal surface for laboratory counters tops, electrical switchboards, and artwork (soapstone carvings).
- Talc is used as an ingredient in paints, plastics, paper, rubber products, roofing materials, ceramics, and insecticides.
- It is most commonly known as the primary ingredient in talcum powder.
- Talc is also used in deodorants and cosmetics and is even found on chewing gum.
Plante, Alan, Peck, Donald, and von Bargen, Donald, 2003, Mineral Identification Key II:
U.S. Geological Survey, 2005a, Minerals Information:
Weisgarber, S.L., and Van Doren, Lisa, 2004, Rocks and minerals everywhere: Ohio Department of Natural Resources Hands on Earth Science No. 6
This activity is adapted from:
The Life Cycle of a Mineral Deposit—A Teacher’s Guide for Hands-On Mineral Education Activities
By Dave Frank, John Galloway, and Ken Assmus
General Information Product 17
U.S. Department of the Interior / U.S. Geological Survey
This report and any updates to it are available online at:
Teachers’ Guide: http://pubs.usgs.gov/gip/2005/17/gip-17.pdf
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