IF YOU ARE AN APARTMENT DWELLER who cannot resist the lure of rocks, the chances are that you have a space problem. Joseph F. Burke, a business executive and amateur mineralogist of New York City, found a solution. He succeeded not only in clearing his den of 500 pounds of specimens but also in discovering a fascinating new side of his hobby.

"The solution," he writes, "is micromineralogy. My present collection contains more than 500 different minerals but it weighs less than two pounds. The entire collection can be carried easily in a briefcase-along with a microscope and other accessories. Instead of the so-called 'bragging rocks' that arouse envy at mineralogy club meetings, you work with chips ranging in size from small marbles to pinheads. You identify these by microphysical and microchemical methods and make them up into 'micromounts' for observation under a low-power microscope. Everything is scaled down but the fun. Some of the finished mounts enter your collection and others are reserved for exchange-just as in macromineralogy.

"I started out as a big rock man, hooked by the same lure that first attracts most amateurs-gem stones. About 20 years ago my morning newspaper announced that huge garnets and tourmalines were turning up in rubble coming out of the Eighth Avenue subway tunnel, then under construction. It seemed an opportunity to get rich quick. After investing a lot of lunch hours in the project, however, my dream faded. I had found only two good specimens and they were not worth much on the gem market. More important, I met several similarly inspired 'excavation prospectors' and we fell into the habit of ranging the city in search of other diggings. The sidewalks of New York may not be paved with gold, but they certainly cover a wide variety of gems. To date the five boroughs have produced modest numbers of garnets, amethysts, agates, tourmalines, emeralds and aquamarines, plus scores of minerals such as rutile, pyrite, magnetite, calcite and some 160 others, a number of which are rare.

"We soon found it difficult to examine a rock without wondering how it got that way and why. Gradually we learned how to take rocks apart and examine their constituent minerals. More than 2,000 different minerals have been described. Some are single elements, gold for example, but most take the form of chemical compounds, such as silicon dioxide, the clear glassy rock commonly known as quartz.

"Weathering and the forces of erosion, we learned, do a lot of the disassembly work for you. Pink granite, for example, often weathers into beach sand that may contain fine grains of clear quartz, black magnetite and ilmenite, and glassy red fragments which are miniature garnets. You find a lot of it along the eastern seaboard. Take a small horseshoe magnet along on your next trip to the beach and pass it over a thin layer of sand spread on a sheet of paper. You will doubtless find that it will attract certain of the black grains. These will be particles of magnetite-tiny lodestones. Float one on a miniature raft of wax paper. If the surface of the water is still, the raft will align one of its dimensions with the earth's magnetic field and you will have a small compass. The other kinds of grains lend themselves to equally interesting experiments.

"By the time the Eighth Avenue subway opened for business, my den had become crowded. Nice specimens are generally embedded in a matrix of minerals which are either in your collection already or in which you have no immediate interest. You take the whole rock home anyway for trimming and dressing at your convenience. So the pile grows, and your space problem grows with it "At about this stage I was presented with a new idea. While I was browsing through the mineral collection of the Staten Island Institute of Arts and Sciences one afternoon, the late William T. Davis, one of the founders, joined me. He asked how my hobby was progressing, and after hearing about the cramped quarters, suggested: 'Why not go in for micromounts?' He pointed out that if your interest goes beyond mere rocks, you can get as much information and satisfaction from chips as from boulders. An inexpensive 10-power microscope will enable you to cut your collection to a small fraction of its present size and, incidentally, free a lot of top-grade material for exchange with other amateurs.

"One look through a borrowed microscope convinced me. It disclosed superb clusters of tiny crystals-far better and more easily identifiable than the few large crystals one might see with the naked eye. Thus the microscope is a powerful tool for identifying minerals.

"To get started in micromineralogy you need little equipment: a rock, a microscope, a small floodlamp for lighting the specimen and a few trimming tools. You first locate the most interesting area in the rock and then chip off and trim a piece. The microspecimen may range from a sixteenth to a half inch across. The dressing tools that will facilitate the job include a small hammer, a vise, assorted dental picks (retired from professional service), a pair of side cutters and perhaps a file or two. Other supplies, such as carbon tetrachloride for cleaning the specimen, will usually be found in the kitchen.

"When cleaned, the dressed specimen is ready for assembling into a micromount: a pillbox of plastic or cardboard in which a short length of cork is cemented for supporting the specimen. It is desirable to standardize the dimensions of your micromounts. Boxes of uniform size stack nicely. If you mount each specimen so that the face you want to look at is at a fixed depth in the box, say a sixteenth of an inch, you can interchange the specimens on the stage of the microscope without refocusing the instrument. This is called 'parfocal' mounting, and it saves a lot of time when, for example, you are searching your collection for a specific type of crystal, surface texture or color to match an unknown mineral.

"My boxes measure approximately one inch square by five eighths of an inch deep. You can procure such boxes from a drug supply house. When purchased by the gross they come in a cardboard container measuring about four by four by six inches. You will also need a supply of corks in the quarter-inch and three-eighths-inch sizes. Other supplies include a tube of quick-drying cement, a bottle of India ink and a sheet of hard-surfaced cardboard. If some of your minerals are speck-sized, you will also want a package of specimen pins (they replace the corks as supports) of the kind used by entomologists for mounting insect specimens.

"In preparing the micromount, first cement a matching disk of cardboard to the small end of a cork. This subassembly, together with the inner face of the box, is then blackened with India ink to reduce unwanted reflection. Next cement the under face of the specimen to the cardboard disk. When the cement has set, measure the height of the mounted specimen and cut it to parfocal length by trimming the bottom of the cork. Then give the freshly cut end a coat of cement and center it in place against the bottom of the box. A pin thrust up through the center of the bottom and into the center of the cork will act as a positioning jig. Finally label the side of the micromount and its top with the serial number previously assigned to the specimen in your notebook.

"Photography affords a further means of compressing your collection. This is not to say that pictures are substitutes for specimens. Modern color prints, however, can prove highly useful on field trips where a bagful of micromounts would prove impractical. Photomicrographs in color are surprisingly simple and inexpensive to make.

"The objective lens of your microscope will serve as the lens of the camera for making these photographs. Details of the camera's construction are illustrated by the group of drawings on the next page. The size of the camera varies with the focal length of the objective and the enlargement that you desire. If you construct the camera around a plateholder four by five inches and use an objective of 20 millimeters focal length, for example, an eighth-inch specimen will fill a negative placed approximately 25 inches from the optical center of the objective. The correct length for the camera is found by multiplying the equivalent focal length of the objective (etched on the barrel) by the desired diameter of the photograph and dividing this product by the diameter of the area of the specimen which is to be included in the picture.

"A simple lens cap will serve for a shutter, because the exposure time will he relatively long-from a few seconds to a few minutes, depending upon the speed of the film and intensity of the light. The exposure must be determined experimentally. The photomicrographs on page 121 were made under a light intensity equivalent to that of a No. 5 photoflash operating at 18 inches. The exposure time for Super XX film was one second.

"In constructing the camera do not fail to include the rectangular diaphragm shown in the center of the lens extension. It protects the negative from light reflected by the walls, which may amount to as much as 4 per cent at grazing incidence, even though the interior is finished in flat black. Bellows-type cameras do not need diaphragms, because the corrugations deflect the incident rays. Make certain, also, that the frosted surface of the ground glass is in the same plane, relative to the plateholder, as that normally occupied by the emulsion. If this precaution is not observed, the pictures will be out of focus. Focusing, incidentally, is accomplished by sliding the specimen toward or away from the objective.

"A bound set of color prints of your collection will multiply its usefulness. On the back of each photograph you should write the name of the mineral, the crystal class to which it belongs and notes on its environment, physical properties, composition, distinguishing characteristics and tests. The set will make an invaluable supplement to conventional field guides, such as Edward Dana's Minerals and How to Study Them and Frederick Pough's A Field Guide to Rocks and Minerals. It will also save time by enabling you to make a quick check of some detail without disturbing the collection.

"In the course of building up a collection of micromounts and identifying specimens, a beginner will discover many fascinating table-top tests. Some minerals, such as crystallized quartz and tourmaline, are piezoelectric: they develop electrical charges on opposite crystal faces when subjected to stress applied either mechanically or by unequal heating. If such crystals are dusted with a mixture of finely powdered red lead and sulfur forced through a silk screen by a blast of air, the particles will separate and settle on the charged faces, the sulfur clinging to the positive face and the red lead to the negative. During the momentary frictional contact between the silk and the powder, the silk has robbed the red lead of some of its electrons and has given up electrons to the sulfur. Thus the two kinds of powder take on charges of opposite polarity.

A homemade bellows closed by two thicknesses of silk stocking makes a convenient duster.

"Other interesting tests make use of the property known as fluorescence. Certain minerals, when viewed under ultraviolet light, glow with characteristic color. Inexpensive lamp bulbs designed especially for emitting ultraviolet light are now available from dealers in electrical supplies. Reference texts written for amateur mineralogists describe many other tests, including those for hardness, chemical behavior, radioactivity and similar identifying characteristics, which will keep an amateur busy for a lifetime even if he limits his prospecting to pebbles found in his own block."

"The only critical requirement in this process is cleanliness. The parts to be anodized must be scrupulously clean, as well as the aluminum conductors leading to the anodizing cell and all vessels used for mixing and storing solutions. Whenever possible, polish the work with No. 400 sandpaper, crocus cloth or a high-speed buff charged with polishing compound. Remove all grease, cutting oils, tool coolants and the like.

"The following equipment should be set up in advance so that you can plunge the work into the bath as quickly as possible after polishing while the surfaces are fresh and uncontaminated. This helps to assure a uniform coating of oxide during the anodizing process.

"The anodizing cell must be made of a substance which will not react with the solution. It can be an old battery jar, large fishbowl, glazed stoneware crock or similar container. It must be large enough so that the work can be immersed completely.

"The cell is filled with a 4 to 6 per cent solution of sulfuric acid. This concentration is not critical. Remember to exercise due precaution. Add the acid to the water, never the water to the acid! Next, connect the work to the anode or positive side of a six-volt storage batter by means of an aluminum conductor. Aluminum clothesline will do, but polish it before you use it. The negative side of the battery is similarly connected by a aluminum conductor to a piece of the purest aluminum available. A large sheet of aluminum kitchen foil will work, but be sure to double it several times to give it strength. Then clamp the foil to the conductor tightly to assure a good electrical connection. The cathode area should be equal to or larger than the area of the work. Remember that you must not permit any metal other than aluminum to make contact with the sulfuric acid solution.

"The work and cathode are now plunged into the solution and permitted to anodize for about 30 minutes. The time is not critical. Be sure the work and cathode do not make contact in the cell, for that would short-circuit the battery.

"In the meantime bring a solution of black Diamond or Rit dye to a boil. One 25-cent package of dye to three quarts of water is about right for pieces the size of a microscope barrel.

"At the end of the anodizing period remove the work from the anodizing solution, pass it under a stream of filtered tap water and immediately plunge it into the boiling solution of dye. Work as quickly as possible. Let the part remain in the boiling dye for about 30 minutes. Upon removal from the solution, the part will present a sickly gray appearance, but don't become alarmed. As soon as it is cool to the touch, wash off the surplus dye and rub the work down with a soft cloth. It will be blacker than a stack of black cats at midnight! Do not attempt to give a polish to any surfaces that may be critical with respect to reflection. With almost no effort on your part, they will take a beautiful polish."

From time to time readers submit amusing mathematical and scientific puzzles to this department. They always turn out to be variations, new or old, of ancient classics, for there is only a handful of basically different puzzles and they have long been known. But some of them may not be familiar to the present generation. We publish this month a classic submitted by Alvin von Auw, a professional journalist and amateur botanist.

Mr. von Auw gives you 12 ball bearings, and remarks that 11 are identical in weight, but the twelfth is slightly off weight. He also gives you a balance, each pan of which has a maximum capacity of five balls. You are permitted three and only three weighings. The object: Single out the odd ball and state whether it is heavier or lighter than the remaining 11.

(If the problem begins to cost you too much sleep, a stamped, self-addressed envelope sent to this department will get you the answer.)

Bibliography

MINERALS AND HOW TO STUDY THEM. Edward Salisbury Dana. John Wiley & Sons, Inc., 1949.

A FIELD GUIDE TO ROCKS AND MINERALS. Frederick H. Pough. Houghton Mifflin Company, 1953.

Suppliers and Organizations

The Society for Amateur Scientists
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