Adopt a Mineral
Dallas Weaver


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Adopt-a-Mineral Project:
Tourmaline and Apatite
Dallas Weaver

www.emporia.edu/earthsci/amber/
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Healing Stones
Dallas Weaver

www.emporia.edu/earthsci/amber/
go336/weaver/healingstones.htm

This webpage project was created for a mineralogy course at Emporia State University. The assignment was to learn webpage creation and present a summary of the properties, benefits, and draw backs of the minerals apatite and tourmaline.

Introduction

Mineralogy is a subfield of the geosciences that includes crystallography and mineral genesis, as well as the physical, chemical, and optical properties of naturally occurring, crystalline solids (S. Aber, pers.comm. 8/2007). The definition of a mineral usually includes the following points: (a) naturally occurring; (b) homogeneous solid; (c) usually of an inorganic origin; (d) definite but not fixed chemical composition; (e) characteristic atomic structure.

In order to understand mineralogy, a background in the discipline is important. Briefly, minerals have been studied for thousands of years and the first known book on minerals was written in 300 BC by a man named Theophrastus, who was a pupil of Aristotle. Over 30 minerals were summarized by 70AD thanks to Pliny the Elder. Since that time, over 4,000 mineral species have been discovered and dozens more are being discovered every year (Wenk and Balakh, 2004). To learn more about two, apatite and tourmaline, read on...

Tourmaline Table of Contents
Apatite Table of Contents

About Tourmaline

The name tourmaline comes from the Singhalese world touramalli which means "mixed colored stones" (Chesterman, 1979). It is actually used to describe an entire group of minerals. These minerals have similar crystal structures but may vary widely in chemical formula due to substitutions of different elements. The general formula for tourmaline is: X1Y3X6(Si6O18)(BO3)3(OH)4. Substitutions for (X) may be Ca or Na. The variable (Y) can be subsitiuted with Mg, Li, Al, Fe, or Mn. (Z) may be replaced with Al, Fe, or Cr. It is because of these substitutions of various elements that there are 14 tourmaline group members. These include: buergerite, chromadravite, dravite, elbaite, feruvite, foitite, liddocoatite, rossmanite, schorl, uvite, and vanadiumdravite. Tourmaline occurs in all different colors and varieties including: chrome tourmaline, manganese tourmaline, nickeloan tourmaline, vanadium tourmaline, and even bicolored and militcolored variets such as the more popular green and pink variety known as watermelon tourmaline (Favero, 2007).
Tourmaline is a cyclocylicate belonging to the hexagonal crystal system. Crystals may range in size from microscopic to over a foot long (Favero, 2007). It has prismatic crystals commonly with a rounded triangular cross section that are striated lengthwise (Chesterman, 1979). Its luster on its faces is vitreous and on fracture is greasy. Tourmaline has a hardness of 7, and can be found in granites, pegmatites, hydrothermal quartz veins, gneisses, and schists (Wenk, and Bulakh, 2004).

Properties/Uses

Tourmaline has two very unique properties called pyroelectricity and piezoelectricity. Pyroelectricity is used to describe the fact that when prismatic tourmaline is heated, its ends develop opposite electric charges (Wenk and Bulakh, 2004). This property had actually been observed before by Theophrastus thousands of years ago. Piezoelectricity is caused when tourmaline develops an electrical charge after it is put under pressure. Even though its primary use is as a gemstone, it is this piezoelectricity that allows tourmaline to have many uses in scientific applications such as pressure-measuring equipment (Favero, 2007).
The image, above and to the right, is of bicolored tourmaline, and taken from www.palagems.com/data/Tourmaline.shtml.

For more information on this webpage, you may email dweaver@emporia.edu.

Return to the table of contents.

References

About Apatite

Apatite is a calcium fluoride phosphate with the chemical formula of Ca5(Po4)3(OH,F.Cl). It sometimes contains other elements such as strontium and cerium. It can be found all over the world in a variety of colors including: green, yellow, brown, red, blue, pink, and white. North American apatite mining sites are in Ontario Canada, San Diego California, and Durango Mexico. The name for the mineral comes from the Greek word "apate" which means "deceit." It is deceitful because it is often confused with other minerals such as fluorite, beryl, and olivine, because of its various colors. Apatite has a hardness of 5, with uneven, conchoidal fracture, and poor unidirectional cleavage. Crystals are usually hexagonal, but are often found in large masses that do not have a specific form but rather a massive habit (Barthelmy, 2007). Its luster can vary from vitreous to greasy (Wenk and Bulakh, 2004). It is usually found in igneous and metamorphic rocks (Barthelmy, 2007).

Uses

Apatite has many beneficial uses. It is used a fertilizer and is a very key role in the human body. It is the main constituent of bones and teeth. Modifications of this mineral make up about 96% of tooth enamel. The crystals are arranged in layers in the enamel for strength against wear and tear. Apatite also accounts for 70% of the substance under enamel: dentine. Along with organic material, apatite crystals are arranged in chaines and make up bone tissue and fibers. The size of these crystals increases with age, in turn causing there to be a lower portion of organic material. This is why bones become less elastic and more brittle in older people. Apatite is also used as a supplement for calcium, magnesium, and phosphorous (Wenk and Balakh, 2004).

Unfortunately, apatite also contributes negatively to the body. Some malignant tumors have had large biogenic apatite aggregations found within them up to 2cm in size. It can also be found in urinary and gall stones along with other phosphates. It can be found in the calcified lungs of patients with tuberculosis, and in the heart tissue, arteries, and aorta of people with heart disease (Wenk, Balakh, 2004).
Image above and to the left is of fluorapatite, beryl, and muscovite. It was taken from www.webmineral.com/data/Apatite.shtml.

For more information on this webpage, email dweaver@emporia.edu.

Return to the table of contents.

References

Related Links
Emporia State University
www.emporia.edu 		Earth Science at ESU
www.emporia.edu/earthsci
Mineralogy Webpage Assignment
www.emporia.edu/earthsci/amber/
go336/assign.htm 		Past Student Projects
www.emporia.edu/earthsci/amber/
go336/webpages.htm

Return to GO336 Student Webpages, www.emporia.edu/earthsci/amber/go336/webpages.htm. Webpage created October 2007; last update December 3, 2007.