Lois Van Wagner
Most students when confronted with a well-formed quartz crystal, or a purple fluorite, or a polished geode, literally jump about demanding to know “Who made this?” and “How did they make this?” and the subject of diamonds and other gems is avariciously at tended to with wide eyes and listening ears. Since the actual atomic structure can be drawn and modeled in a wide variety of mediums even the more humdrum aspects can be made inviting. And the chemical concoctions that can result in some homemade crystals bring out the white-coat scientist in even the most reluctant student. Many of the students own small personal calculators that are solar-powered, or have seen the advertisements in discount store circulars for solar powered exterior lighting. These obje cts provide a good jump-off point for discussions about crystals and technology.
My unit on crystals will be divided into three categories covering three areas of study. The first area will deal with the actual structure of crystals beginning with a look at the atom, some simple atomic drawings (Bohr models) of elements, and a study o f the periodic table of the elements. Next we will look at compounds and their bonds. This will lead to the understanding of how crystals “look” and the shapes they can take. Within this section we will draw and construct in three dimensions paper models of six of the basic crystal shapes. We will also grow some of our own crystals in the laboratory.
The second major heading in my unit will focus on minerals. We will learn about the characteristics of a mineral: the chemical composition, mineral color, luster, cleavage, hardness (and how this property is related to crystal structure), and specific gra vity. The characteristics of minerals lend themselves nicely to a mineral identification lab, and a lab on specific gravity of minerals and selected rock samples. Some of the other topics in this section will include a study of the various forms of quartz ; gems, especially diamonds; the formation of mineral crystals—by igneous, sedimentary, and metamorphic processes; and some stories of famous (or infamous) gems.
The final section of this unit will delve into the uses for crystals which modern technology has fostered, specifically solar cells, transistors, and liquid crystals.
The unit is designed for the middle school age level, specifically for the eighth grade Earth Science curriculum. In the two years that I have used this curriculum unit with my eighth grade classes I have amplified or omitted sections depending on the int erest and abilities of the various classes. In this way I have been able to use the unit with students that range in ability from very high to very low.
Throughout this paper I am indebted to the teaching and guidance of Dr. Werner Wolf and to the following books and sources:
(figure available in print form)
(where p stands for proton number, e stands for electron number, n stands for neutron number, and K and L represent the first two electron energy levels.)
After drawing out a few, or many, of the Bohr models the children will notice that some of the models have an outer shell that only needs one or two more electrons to be filled, and that others have one or two electrons that seem to hang awkwardly by them selves in their outer shell. These conditions can of course be used to develop an understanding of the terms metal and nonmetal. Since the children can “see” the electrons they can judge their availability for donating or receiving. This technique makes e asy work of explaining compounds and their chemical formulas. It also aids in the explanation of ionic and covalent bonding.
(figure available in print form)
(figure available in print form)
The bonds of compounds can influence some substances physical properties. And bonds exist not just between individual atoms but also throughout a crystal. We can look at two forms of the element carbon for an example. Graphite is a slippery black solid, t he bonds form sheets of carbon which slide loosely over one another. Diamond on the other hand is a hard, clear crystal with tight tetrahedral bonding that holds the carbon atoms of diamonds securely in place. The difference can be seen below in the illus tration.
(figure available in print form)
Further investigation of the importance of chemical bonds can be accomplished by a study of sugar and salt crystals. By comparing melting points and ease of crushing some simple inferences can be made about their bonds. Directions for this experiment are to be found in Appendix 1, Activity 1.
Since most of their crystals will be formed by solution the student needs to add the words solute, solvent, and solution to his vocabulary. The solute is the substance being dissolved and the solvent is the substance doing the dissolving. A solvent can ho ld in solution just so much of the solute. At this point we say the solution is saturated. If there is less solute in the solution than it would ideally hold we would then say it is an unsaturated solution. And in some cases such as when we heat the solve nt we can continue to add solute and it will dissolve. When the heat source is removed and the solution’s temperature falls the extra solute may remain in solution. This fragile situation is called supersaturation and is the basis for our crystal growth experiments.
Solubility, or the amount of solute which can be dissolved in the solvent, is affected by a number of factors, one of which is the temperature of the solvent. Generally speaking we increase solubility of solid solute when we increase the temperature of the solvent. (This is not true of the solubility of gases in a solvent as is witnessed by anyone who has sipped a glass of warm, flat soda.) In Appendix 2 there are some solubility figures which the student can use to set up graphs of solubility curves.
Crystal growth is a very orderly and regulated process. A crystal grows from the southside with the atoms of the compound being added according to a very specific pattern. If there is not enough space for the crystal to grow unhindered it will increase on ly until it meets something which gets in its way and then stop. Often many small crystals begin forming at the same time, and they grow until their edges meet at varying angles. They do not join to form a single large crystal but rather remain a jumble of small individual crystals forming a polycrystalline mass. The adjoining faces of the crystals are called the grain boundaries. These boundaries are particularly evident in metals which have formed by fairly rapid cooling of the molten form. During the c ooling process innumerable small crystals form and grow until they bump into a neighboring crystal.
Crystals can form from the cooling or evaporation of solutions, or from the cooling of molten solid, or the cooling of vaporized substances. In Appendix 3 you will find a number of experimental techniques for demonstrating crystal growth and for student p articipation in crystal growing.
Many crystals in nature demonstrate this mixed crystal condition in the replacement of aluminum by chromium or sometimes iron. Rubies are a good example of this, being composed of aluminum oxide with chromium replacing some of the aluminum, and also sapph ires which replace the aluminum with titanium and iron.
In some cases a slightly different atomic substance can enter a crystal but only in small quantities. This is called a substitutional impurity. A most relevant example of this is substitution of phosphorus or boron atoms in silicon crystals. These “impure ” compounds are used to make transistors for electronic instruments.
Sometimes a different kind of impurity enters a crystal. These foreign atoms may be very small compared to the host substance and fit in between the orderly arranged host atoms. If the host substance has a generous size pattern the invading atoms could be as large as the host atoms themselves. The additional atoms are called interstitial impurities. A well known example of this is carbon and iron, which makes steel.
A third kind of defect could be called a vacancy. This results from very rapid crystal growth during which some of the atomic sites are simply not filled. The milky or veiled appearance of home-grown crystals, however, is caused by very large openings called voids. It generally occurs when the evaporation of solvent proceeds too rapidly and incomplete crystallization happens. The white coloration is caused by the presence of a liquid solution that is trapped in the open spaces of the crystal. Vacancies on the other hand are far too small to be visible.
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Minerals are natural substances that are inorganic and not the result of any living process, therefore ruling out coal, oil, or pearls. It must also have a specific chemical formula, made up of atoms in a definite ratio. In addition the atoms must have a definite and specific arrangement in space. It is because of these characteristics that minerals have unique properties which can be used to differentiate them from one another.
Many minerals are made up primarily of elements which impart no strong color of their own and only minute amounts of a coloring agent can have striking results. Some color guidelines are: red may indicate the presence of chromium or hematite, green can in dicate chlorite or chromium, and blue can indicate the presence of titanium or titanium and iron. The presence of copper ions can result in shades of green or blue and manganese can result in shades of red. It is sometimes helpful to determine the color of a mineral’s streak by rubbing the sample on an unglazed porcelain streak plate. This powdered residue is often more accurate in indicating true color and many mineral identification handbooks include a list of streak colors.
Hardness of a mineral is shown by its resistance to being scratched. This is related to the crystal structure in that the more tightly bonded the atoms the harder the surface resistance to being etched will be. Diamond is the hardest mineral but is not re adily available for student experimentation. Corundum is the next step down and it inexpensively available. In 1812 Friedrich Mohs devised a rough scale of hardness that is invaluable in mineral identification. Diamond at number 10 is the hardest, and tal c at number 1 is the softest. The intervals between the numbers are not equal, however, and the difference between corundum at 9 and diamond at 10 is greater than the entire range of 1 to 9!
|1. Talc||6. Feldspar|
|2. Gypsum||7. Quartz|
|3. Calcite||8. Topaz|
|4. Fluorite||9. Corundum|
|5. Apatite||10. Diamond|
Luster is that mineral property which indicates the way light is reflected from the surface of the sample. Some luster terms are: glassy, metallic, greasy, pearly, or satin-like. These are all terms the students are familiar with and can also be used in c onjunction with an identification manual.
(figure available in print form)
Another means of identifying minerals is specific gravity. This measurement can be the most helpful identifying characteristic of all as it is apt to be the most reliable. The students can have a very interesting lab built around this property. Directions for this lab are in Appendix 1, Activity 4.
The story of Archimedes and his quest for a way to determine the value of the king’s crown is a sure-fire attention-getter to start the lesson. According to the legend, in about 250 B.C. Archimedes was given the task of determining if a crown belonging to King Hiero was pure gold or only an alloy of gold and silver. It is said that upon easing into his tub the bath water spilled over the edge and it came to him that the volume of water lost was the same as the volume of his body, and he could use the same technique to determine the volume of the crown. Since it was known that gold and silver have different densities, the only thing that would remain would be to take an accurate measure of the weight of the crown and divide this by the volume of the crown. The resulting density figure could be compared with the density of gold, and the truth would be known. It is said that with this revelation, Archimedes leaped from his bath and ran, forgetting the state of his undress, through the streets of Syracuse in Sicily exclaiming, “Eureka!—I have found it!” on his way to the palace! A sad footnote to the story is that the crown was indeed not the pure gold it had been portrayed as, and the unfortunate merchant met an uncomfortable end. Or so they say.
Carried one step further, the concept of specific gravity is based on the physical law that an object immersed in water loses as much weight as an equivalent volume of water would weigh. With a spring balance and a water pan the students can determine the specific gravity of a variety of minerals. Experience has shown that fairly large specimens will give the best results. See Appendix 1 for directions for labs on this and related topics; Activities 4, 5, and 6.
In 1880 the Curies discovered another peculiar property of quartz while studying the electrical conductivity of crystalline bodies. They discovered that pressure on plates of quartz caused a deflection of the needle on a sensitive electrometer. This is ca lled the piezoelectric effect. It occurs when the crystal is squeezed slightly out of shape and then springs back. This shape change actually affects the crystal at the atomic level causing a movement of ions, with their attendant electric charges. This m otion of the electrically charged particles constitutes flow of electrons, or electricity. This particular characteristic is now used to control and stabilize the frequency of a radio transmitter or to regulate watches.4
Another form of quartz known and valued for its beauty is amethyst. This mineral is almost pure SiO2 with only a trace of iron. As the amount of iron increases, so does the intensity of the violet color, so it is believed to be the coloring agent. Accordi ng to folklore the amethyst gives its wearer great power, increased intelligence, and strength.
Smoky quartz does not differ from clear quartz in chemical composition. In fact when it is heated to very high temperatures the “smoky” color vanishes, and it looks identical to clear crystalline quartz. The color can be restored by treating the crystal w ith a beam of x-ray radiation. Scientists believe that the color of smoky quartz is a result of natural radiation in the earth.
Agate is a common form of quartz which does not have any external evidence of its crystal nature. The extremely tiny crystalline particles are so intergrown that they appear smoothly mixed. Agate is used decoratively and as jewelry, especially in the onyx form.5
A form of quartz that is unique and appears to be most “un-quartz like” is the opal. It contains a rather large percentage of water, ranging from four to twenty percent. And a complex internal structure of microscopic silica fitted together in a lattice-p attern results in diffraction of the light hitting it, forming rainbows of brilliant color as the gem is rotated. Opal is a low-pressure and low-temperature mineral and is formed at the earth’s surface by deposition from ground water or by the evaporation of hydrothermal, or hot water, springs as they rise to the surface and cool leaving opal mineral behind. Because of the rather large amount of water present in opal, it tends to be relatively soft (5.5 to 6.5) and low in specific gravity. These qualities limit its use as a gem, and it is usually found mounted in pendants and pins where the stone is relatively protected.6
Man is not at a total loss in this field. Currently we are producing some 44,000 pounds for industrial use annually by a process developed by H. Tracy Hall for the General Electric Research Labs in the early 1950s. His process involved a mixture of graphi te powder and an iron compound placed in a hydraulic press. This press was able to generate a force of more than 1.5 million pounds per square inch! To that was added an electrical current which heated the mix to over 4,800 degrees Fahrenheit. From this w as produced low quality diamond grit used widely for industrial purposes as an abrasive.
Gem quality diamonds are another story. Instead of the less expensive carbon sources which are used in the manufacture of industrial diamonds, the feed material for gem quality diamonds is the industrial grit, and the pressure and temperatures must be mai ntained for long periods of time, up to a week. From this we can obtain gem quality diamonds of up to one carat, but unfortunately the cost of manufacture is higher than the present cost of mining the natural stones.7
Natural diamonds are thought to be formed deep within the earth, probably 90 to 120 miles down within the upper regions of the mantle. Here pressures of 975,000 pounds per square inch and temperatures of at least 2,700 degrees Fahrenheit may cause carbon atoms to crystallize into tetrahedral shapes of great strength. Diamond is more resistant to scratching than any other mineral, only another diamond can mark it. It is resistant to acids and alkalis. It is brilliant and has very high dispersive qualities which result in the flashes of light reflecting from the cut stone. Dispersion is the ability of a substance to separate white light into its component colors just as a prism or water droplets forming a rainbow. It also has a relatively high specific gravity, 3.5, which results in it being found in placer deposits, those areas in stream beds where heavy and often valuable particles settle out and collect in quantity.
Diamonds were first found in India and for thousands of years this was the only source. They were not mined but rather found in stream gravel and alluvial deposits. Some famous stones from India with fascinating histories are the Koh-i-nor and the Great M ogul. In the early 1700s diamonds were discovered in Brazil. Men panning for gold found clear pebbles that were later recognized as diamonds! Many of these South American gems were shipped to India to be sold in their markets to Europeans. As India’s sour ces began to dry up, Brazil became more acceptable in the world’s eyes as a diamond source. And so for a while Brazil was the principal producer of diamonds. Even today many fine gemstones come from there.
The most extraordinary diamond finds have occurred only within the last one hundred years or so. In 1866 a Boer farmer’s son found a shiny pebble on a river bank in South Africa. It turned out to be a 21.5 carat diamond! Adventurers from all over the worl d descended on the site turning it into a free-for-all not unlike the American gold rush. Diamonds were recovered from the river bank, the surface soil, deeper “yellow ground,” and finally at depths of fifty to sixty feet, the “blue ground.” This rock is the original matrix which the diamonds formed in more than 15 million years ago. Diamonds have also been found beneath the beach sand at the mouth of the Orange River and now mining is being done in the Atlantic Ocean in that area.8
Very few diamonds have been found elsewhere in the world. An occasional gem has been found in the American midwest in glacial deposits or in dunes. And in Arkansas some have been found in their rock matrix similar to the blue ground of South Africa. They have also been found in the Soviet Union, but not much is known about these.
When tectonic processes, volcanic activity, or deep burial subject rock to great heat and pressure, metamorphic forms may result. The partial melting of the parent rock allows specific minerals to escape and move to areas where they concentrate into gems. Examples are garnets, which can be found here in Connecticut, and the famous Burmese rubies and sapphires.
Displaying geodes to the students is an extremely valuable tool as it is obvious to the group that the individual perfectly formed crystals could not have been carved out by man. This idea of the human manufacture of crystals, especially the particularly beautiful quartz or pyrite crystals, is quite common among students at this grade level.
(figure available in print form) As the conduction electrons move in to fill in the holes, a peculiar thing happens. The boron atoms which take up the electrons in their holes now become negative ions! And the phosphorous which has given the conduction electron up now becomes a positive ion! This results in a boundary called the p-n junction where holes with their positive charge and electrons with their negative charge are repelled by the charged ions that set them loose. So the excess conduction electrons are unable to move across the boundary to fill in the holes. This results in electrons building up in the n-type layer and holes will collect in the p-type layer.
Electrons move toward the p-type side and holes (positive) move toward the n-type side until a dynamic equilibrium is reached. Ionized boron repels further movement of electrons and ionized phosphorus repels further movement of holes (positives).
(figure available in print form)
When photons strike the solar cell, bonded electrons are bounced right out of their positions creating many more conduction n-electrons and holes on both sides of the junction. Since there are already so many electrons on the n-type side and so many holes on the p-type side, the additional new ones are only a tiny proportion; but by making new holes on the n-type side and new conduction electrons on the p-type side, the solar cell is unbalanced. The electrons from the p-type side move across the junction creating a flow of electrons, or electricity! This flow moves electrons out through the n-type layer onto a conductive wire grid which is connected to a circuit that is completed by an attachment to the p-type layer.12 Read more about this fascinating but complex topic in Chalmers’ article or Swan’s book.
Solar cell circuit in which conduction electrons move toward the n-type crystal where they travel to the current collector on the surface of the cell and move through the external circuit to the p-type crystal area.13
(figure available in print form)
More complex wiring and liquid crystals with helical (spiral) axis positions can display 5-32 elements per electrical lead and are used for personal computers. The newest experimental versions are capable of producing TV picture displays on a flat substrate.
Liquid crystals are true liquids but also have some solid properties. Their internal order is very delicate and can be changed by a weak electrical field, magnetism, or even temperature variations. Noticeable optical effects are the result of re-arrangeme nt of the molecules and the resulting changes in refraction (light-bending), reflection, absorption, scattering, or coloring of the visible light from their surface. Liquid crystals modify the ambient light rather than emit their own light and therefore r equire minimal amounts of power. A typical LCD (liquid crystal device) uses one microwatt per square centimeter of display area.16
A very simplified diagram below shows the effect of an electric current on liquid crystal molecules. This change is visible due to its effect on light waves.
(figure available in print form)
Some liquid crystals are sensitive to temperature, and are used as a component in thermometers. They can be used in diagnostic tools to detect cancers, pulmonary disease, and vascular diseases. Their dramatic color variations are caused by an actual helical swing of 360 degrees by the molecules! The diagram below shows this 360 degree reorientation process.17
(figure available in print form)
A uniform starting position for the crystals is vital to their usefulness. Liquid crystals can be aligned by “rubbing” of the substrate. Until recently this was poorly understood but used as a standard practice anyway. It is now known that the rubbing res ults in microgrooves which serve to orient the molecules.l8
Although liquid crystal technology has only recently been exploited by man for diagnostic tools, displays, new materials such as kevlar, and oil-recovery technology, nature has used these peculiar molecules in living systems right along. The structure of cell membranes and some tissues are liquid crystals. Hardening of the arteries is a result of the deposition of liquid crystals of cholesterol, cells involved in sickle cell anemia have liquid crystal structure, and on a brighter note, it may soon be poss ible to change the solid form of a gall stone into a liquid crystal form that can be flushed from the body.19 For further information see the Brown or Kahn articles.
The technological development of crystals has taken off in this generation from semiconductors to transistors to integrated circuits to microchips. Always getting smaller but with vastly increased information handling abilities. They are the mainstay of t he space and military industries, making possible the impossible in distant space travel, satellite technology, and weapons’ accuracy.
Solar cells are becoming more efficient and more common, and as our energy problems increase, student interest in solar technology has also increased. And the liquid crystals in our students’ watches and pocket calculators are just one more bit of technology waiting to be explained to our students.
There are many very helpful books and articles which can aid the reader in his or her understanding of these interesting, complex topics. Many of these have been listed in the bibliography, but I would like to specifically recommend the Holden book, The Nature of Solids, and the Chalmers article, “Photovoltaic Generation of Electricity,” as two excellent readings with which to begin. They will provide you with the information you will want to feel confident about teaching about crystal technology.
All of the books and articles that are specifically referred to in the text of this unit are available in book or reprint form at the Yale-New Haven Teachers Institute office on Wall Street, New Haven.
Crystal model outline sheet #2
(figure available in print form)
Density = mass/volume
*Important Information: one milliliter = one cubic centimeter (1 mL = 1 cm3)
|steel nail||lemon juice or dilute|
|hardened file||hydrochloric acid (Use acid only on samples kept at demonstration table—do not contaminate your samples at your desk.)|
1.What is the solubility of sodium nitrate at 60 degrees Celsius?
2.What is the solubility of potassium chloride at 90 degrees Celsius?
3.What is the solubility of sodium sulfate at 50 degrees Celsius?
4.What is the solubility of sodium nitrate at 30 degrees Celsius?
To grow crystals from an alum solution dissolve 4 teaspoons of alum powder in a half cup of hot water. Stir until all of the powder dissolves. Cover the beaker with paper or cloth to keep the dust out and slow evaporation. Crystals will begin to form on the bottom of the container. It is important to keep your solution free from drafts or temperature changes. If your room has a widely varying temperature range, set the beaker in a large bucket of water, being careful not to get extra water in the beaker. The water will help prevent any rapid temperature changes.
When some good size crystals have formed, pour off and save the solution and carefully pick out the best crystals with tweezers. Dry the crystals and the tweezers well. Now pour the solution back into the beaker with the remaining crystal masses and gently reheat and redissolve the solute.
The next step is a real test of your dexterity! You must fasten the crystal to a thread, either by means of a slip knot or with a minuscule spot of glue (Duco cement is good). Suspend your hanging crystal “seed” in the cooled solution and cover the top. It is important to be sure there are no extraneous crystal grains on the sides of your crystal seed, on the thread, or in the container. Growth of your seed will be impeded by them. Again place the beaker in the water bath to control temperature during the growing time. This process would result in a single, large, well-formed crystal.20
Other substances which can form nice crystals are borax, salt, sugar, copper sulfate, and Epsom salts. The amount of solute will vary, but you can determine the appropriate amount by trial and error or by checking one of the books given above.
To grow crystals from a melt, obtain some salol (phenyl salicylate, HOC6H4COOC6H5) from a drugstore. Put a small amount on a glass slide or sheet of aluminum pie plate, and heat it with a candle. Since it melts at 42 degrees Celsius, you will not need much flame. As it cools, put a tiny grain of salol powder on the melted salol; this will act as a seed for the crystal to grow around.21
To grow crystals from a vapor, obtain some naphthalene (moth-flakes, C10H8). CAUTION—NAPHTHALENE IS VERY FLAMMABLE AND MUST NOT BE HEATED NEAR AN OPEN FLAME! Woods suggests placing a few flakes in a tall glass jar and placing a loose cover (aluminum foil) on top. Place the base of the jar on a lighted 100 watt bulb, and soon you will see the rising vapor sublimating (changing from vapor to solid) onto the top sides of the container. This experiment should be done in a very well ventilated room, preferably within a vented hood.22
3A. Holden and P. Morrison, Crystals and Crystal Growing, 38-40.
7J. Arem, Man-made Crystals, 45.
8C. Hurlbut, 212-216.
9P. O’Neil, Gemstones, 82.
11B. Chalmers, “Photovoltaic Generation of Electricity,” 36.
12C. Swan, Suncell; Energy, Economy, Photovoltaics, 56.
13B. Chalmers, 38.
14A. Holden, Nature of Solids, 216-218.
15F. Kahn, “Molecular Physics of Liquid-Crystal Devices,” 66.
17G. Brown and P. Crooker, “Liquid Crystals,” 32.
18F. Kahn, 70.
19G. Brown and P. Crooker, 36-37.
20E. Woods, Crystals—A Handbook for School Teachers, 26.
———. Rocks and Minerals. New York: Bantam Books, 1973. A well-illustrated paperback handbook with descriptions of atoms, bonds, and crystal structures. The minerals are grouped by chemical composition and are beautifully illustrated.
Brown, G. and Crooker, P. “Liquid Crystals.” C&EN (January 31, 1983): 24-38. Hard to read, but complete discussion of liquid crystals.
Cady, W. “Crystals and Electricity.” Scientific American (December, 1949): 46-51. An understandable, concise discussion of piezoelectricity, its uses, and how it works. Highly recommended.
Dana, E. Minerals and How to Study Them. Revised by C. Hurlbut. New York: John Wiley and Sons, 1949. Old but very complete guide to minerals. Crystallography discussed in detail and it has a convenient compact size and is easy to understand.
Desautels, P. Rocks and Minerals. New York: Grosset and Dunlap, 1974. Outstanding demonstration photos—double page size, 16” x 12,” with a brief description of photo subjects and related varieties.
English, G. Getting Acquainted with Minerals. New York: McGraw Hill Book Company, 1958. Textbook of mineralogy with an identification key based on hardness and luster.
Hewitt, P. Conceptual Physics. Boston: Little, Brown and Company, 1985. General college-level physics text.
Hittinger, W. “Metal Oxide Semi-Conductor Technology.” Scientific American (August 1973). Advanced level discussion of semi-conductors (bipolar and unipolar) and integrated circuits.
Holden, A. The Nature of Solids. New York: Columbia University Press, 1965. A basic, comprehensive guide to the physics and chemistry of crystals. It is a good introductory book for a study of crystallography.
Holden, A., and Morrison, P. Crystals and Crystal Growing. Cambridge, Mass.: The MIT Press, 1982. A well-written guide to crystals, covering everything from the physics and chemistry of crystals, structures, and uses to the actual growing techniques. Enjoyable reading and my first choice recommendation.
Hurlbut, C. Dana’s Manual of Mineralogy. New York: John Wiley and Sons, 1959. A detailed text book, but has an excellent key to identify minerals, and several useful pages of tables.
———. Minerals and Man. New York: Random House, 1970. This book is a masterpiece of information and color photographs which reads like a novel. 304 pages of detailed information and stories which will certainly hold your interest and attention. Highly recommended.
Kahn, F. “The Molecular Physics of Liquid-Crystal Devices.” Physics Today (May 1982), pp. 66-74. A very technical discussion of liquid crystals with helpful diagrams.
Kirkaldy, J.F. Minerals and Rocks. Poole, England: Blandford Press, 1963. Handbook format with many color photos and some descriptive geology. An important feature is the extensive glossary of terms.
McGavack, J. and LaSalle, D. Crystals, Insects, and Unknown Objects. New York: The John Day Company, 1971. A book written by a former Science Supervisor and Assistant Superintendent of Schools in New Haven, focuses on hands-on learning techniques and incorporates a unit on crystal growing and its creative approach to learning.
O’Neil, P. Gemstones. Alexandria, VA.: Time-Life Books, 1983. A richly illustrated, well written book that covers the formation, the composition, and the history of gems. Highly recommended, enjoyable.
Pearl, R. Gem, Minerals, Crystals, and Ores. New York: Odyssey Press, 1964. Interesting discussion of gem cutting. Outstanding glossary of mineral terms, crystal terms, mineral name origins, mining and geology terms, as well as multitudes of listed minerals and ores.
Ransom, J. The Rock Hunter’s Range Guide. New York: Harper and Row, 1964. Good for beginning rock collectors. Explains the use of geologic maps and where to get them, how to prospect new locations, and listings of mineral sites for each state.
———. A Range Guide to Mines and Minerals. New York: Harper and Row, 1964. A more comprehensive guide to mineral collecting with lists of abandoned mines in the United States.
Read, P.G. Dictionary of Gemmology. London: Butterworth Scientific, 1982. Comprehensive dictionary whose recent publication date makes it useful.
Swan, C. SunCell: Energy, Economy, Photovoltaics. San Francisco: Sierra Club Books, 1986. A comprehensive guide to solar energy dealing with everything from the physics of the cells, the practical uses, the future uses, to the politics and economics of solar energy.
White, J. Color Underground. New York: Charles Scribner Sons, 1971. Beautifully illustrated picturebook of crystals. Large pictures good for displaying with each crystal described and explained. Good for student or teacher use.
Woods, E. Crystals—A Handbook for School Teachers. The International Union of Crystallography, 1972. A small but very useful book giving step-by-step directions for growing a wide variety of crystals plus an assortment of things to do with the crystals you grow. Highly recommended.