PETITE MINERALS

In the long ago when you and I could go searching for mineral specimens unrestricted we were quite particular about what we collected; only the very choicest material in rather large size was considered worth bringing home. Even if an especially attractive group of crystals happened to be a bit larger than what we had been in the habit of collecting, we were not too much disturbed. Conditions have changed; some collecting localities are completely exhausted, others are hopelessly buried under the encroachment of expanding communities. Before, if you thought you could afford to buy a specimen once in a while, a modest sum would purchase an attractive addition to your collection. Today the growing scarcity of fine minerals is reflected not only in the variety offered but in the price. Once specimens which fall within the range of the two smaller sizes collected now, referred to as miniatures, would have been regarded disapprovingly, characterized as something no one wanted. Though large and showy specimens may be had now, another condition has developed which favors smaller sizes. Homes today are not as spacious as they once were. Minerals, no matter how kept, whether in display cases or in tiers of drawers or both, need lots of space. So the smaller specimen has found its place partly for that reason. However, the popularity of miniatures is not dependent wholly on the adaptability to conditions. We have learned that by careful selection and arrangement an eye-catching colorful display can be created with these small specimens, especially those called thumbnails. So between force of circumstances and our ability to make the best of conditions collectors are displaying and enjoying minerals quite as enthusiastically if not more so than when everyone concentrated on large, spectacular pieces.

Today the growing scarcity of fine minerals is reflected not only in the variety offered but in the price. Once specimens which fall within the range of the two smaller sizes collected now, referred to as miniatures, would have been regarded disapprovingly, characterized as something no one wanted. Though large and showy specimens may be had now, another condition has developed which favors smaller sizes. Homes today are not as spacious as they once were. Minerals, no matter how kept, whether in display cases or in tiers of drawers or both, need lots of space. So the smaller specimen has found its place partly for that reason. However, the popularity of miniatures is not dependent wholly on the adaptability to conditions. We have learned that by careful selection and arrangement an eye-catching colorful display can be created with these small specimens, especially those called thumbnails. So between force of circumstances and our ability to make the best of conditions collectors are displaying and enjoying minerals quite as enthusiastically if not more so than when everyone concentrated on large, spectacular pieces.

In competitive mineral exhibits the miniature classification is restricted to specimens more than one inch square but not over two inches square. Above two inches they are considered cabinet size. Sometimes the one-byone specimens are referred to as miniatures, but again taking as the standard the classification adopted for competitive exhibits, these are thumbnails. To qualify in competition they must be entered in a standard box of fifty compartments. The average collector does not in-terest himself in material smaller than the thumbnails (abbreviated T/n) except when it is necessary to take something very small because the material is rare and unobtainable in larger pieces. However, the classification is carried down just one more step to the micro specimens; the Lilliputians, sometimes called the flowers or fairies of the mineral kingdom. They may be called micro specimens or micro mounts; the expressions refer to the same thing. There are not many collectors of micro mounts because to be appreciated they must be studied under a microscope, and microscopes have always been expensive.

terest himself in material smaller than the thumbnails (abbreviated T/n) except when it is necessary to take something very small because the material is rare and unobtainable in larger pieces. However, the classification is carried down just one more step to the micro specimens; the Lilliputians, sometimes called the flowers or fairies of the mineral kingdom. They may be called micro specimens or micro mounts; the expressions refer to the same thing. There are not many collectors of micro mounts because to be appreciated they must be studied under a microscope, and microscopes have always been expensive.

Sooner or later everyone who collects and studies minerals is impressed by the abundance if not predominance of small crystals. A specimen may be of value just for the small crystals it shows or these tiny glistening forms may be only incidental or wholly unrelated to the specimen as a collector's item. At the opposite extreme in size there are a few very large crystals, referred to many times in mineralogical literature. For exaniple, the more than 3000 pounds of smoky quartz crystals removed from a single cave or "pocket" in Switzerland more than one hundred years ago. Many of these giants weighed from 50 to 100 pounds. The very largest was thirty-two inches long by thirty-six inches in circumference, tipping the scales at two hundred twenty-five pounds. The other classic example of a giant crystal is the huge spodumene in the Etta Mine, Keystone, South Dakota, which is fortyseven feet long, five feet in diameter, estimated to weigh about ninety tons. During some of the more recent exploratory work on pegmatite dikes in Arizona spodumene crystals more than three feet long by twenty inches in diameter have been uncovered.

Forms may be only incidental or wholly unrelated to the specimen as a collector's item. At the opposite extreme in size there are a few very large crystals, referred to many times in mineralogical literature. For example, the more than 3000 pounds of smoky quartz crystals removed from a single cave or "pocket" in Switzerland more than one hundred years ago. Many of these giants weighed from 50 to 100 pounds. The very largest was thirty-two inches long by thirty-six inches in circumference, tipping the scales at two hundred twenty-five pounds. The other classic example of a giant crystal is the huge spodumene in the Etta Mine, Keystone, South Dakota, which is fortyseven feet long, five feet in diameter, estimated to weigh about ninety tons. During some of the more recent exploratory work on pegmatite dikes in Arizona spodumene crystals more than three feet long by twenty inches in diameter have been uncovered.

Because tiny crystals, almost without exception, are more nearly perfect in form than much larger crystals they are desirable natural material for studying that branch of mineralogy known as crystallography. In nature it is only rarely that a crystal conforms to the ideal shapes it should assume. Every characteristic of normal crystals, the color, brilliance of faces, certain distinguishing marks on the faces, and the sharpness of the interfacial angles is outstanding on tiny crystals.

Naturally the faces of small crystals are so small that they cannot be seen except by some degree of magnification. Because of their positions, most always in groups in a cavity, it is rarely possible to identify all the possible faces on any one crystal. Though the collecting and study of micro mounts may be treated fundamentally as the study of crystallography it should not be taken for granted that there is no other enjoyment to be had from viewing m/ms. Crystallography is a somewhat compli- cated phase of mineralogy but there are hours of enjoyment in just marveling at the perfection of form and brilliance of colors in these tiny jewels. Preparing the material has its exciting phases; choosing the material, shaping and finally mounting is a fascinating pursuit.

The first mention of tiny crystals being observed by magnification is in a very rare old book entitled "Micrographia of Minute Bodies Made by Magnifying Glasses," written by Robert Hooke, London, 1667. He examined many things, among them cavities in flint in which he found some mineral crystals though he could not identify them. About 1870 Rev. George S. Rakestraw and George W. Fiss, in separate communities and unknown to each other, began to make micro mounts. Some years later C. S. Bement, who assembled one of the most notable mineral collections in the United States, became interested in the novel method of mineral study. He began to furnish choice material to Mr. Fiss to mount, one for himself and one to be retained by Mr. Fiss. About 1911 Mr. Fiss bought the Bement collection which he sold a year later to A. F. Holden, who presented the entire collection of 2300 specimens showing 475 species to Harvard University. In 1925, Mr. Fiss died at the age of ninety-one after having made many valuable contributions to the science of mineralogy because of his many discoveries. His collection was retained by F. J. Kelley, who gave the Fiss microscope and accessories to the Academy of Natural Sciences of Philadelphia. Other notable collections of micro mounts were made by well-known students of mineralogy of half a century ago. Among them were the late Dr. George F. Kunz, famous as the world's gem expert, George L. English, collector, dealer, and author, William W. Jefferis, another discoverer and contributor to the field of science. Other collections, less spectacular, were made about the same era but were not so well known. Micro mounts are not adapted to display, hence they are seen only very rarely in museums. However, such material has been of great help in the continued advances being made in the study of minerals.

Nearly every one of the early micro mounters had his own method of mounting specimens. Mr. Fiss mounted his in a small thin-walled brass cell cemented to a glass slide. Rev. Rakestraw used a small rectangular paper box. Subsequently he developed what is known today as the standard m/m box, 7% x 78 x % deep, having a slip-on cover. Since 1942 the paper boxes have been unobtainable. As a substitute we now have a clear plastic box of exactly the same size, which is more durable than the paper box. The supplier will furnish, at no extra cost, a black paper liner which prevents reflection from the highly polished sides. Indentical boxes of black opaque plastic are obtainable but there is the objectionable feature of reflection, a serious handicap when examining a micro mount.

A microscope is the only major piece of equipment needed to indulge in this fascinating hobby. Generally speaking, microscopes are expensive, which accounts for the fact that there are not more micro mounters. For studying micro specimens the ideal instrument is the binocular type, which gives a three-dimensional image. However, a little experience coupled with the ability to project in your mind the third dimension will enable you to get an abundance of enjoyment using the conventional monocular 'scope, much less expensive and more plentiful. Imported instruments of the binocular type, of fine

material and good workmanship, are available now for as little as one hundred dollars. This is about the investment made by the average photographic enthusiast for either black and white or color photography. To this he must add the cost of each new roll of film which in the long run amounts to much more than the cost of supplies the micro mounter needs. Much of the micro material can be collected, but perhaps it may be desirable sometimes to purchase a small specimen which would hardly please a collector but from which one or more very good m/ms may be removed.

Good illumination is a must. There is a wide variety of illuminating devices on the market, made by the manufacturers of microscopes, but they are almost all expensive. Besides the cost there is another objection: the light comes from one direction, hence there is always a part of the specimen in shadow. Four 110-volt, 8-watt lamps in sockets used on Christmas trees mounted in a suitable block of wood as shown in the illustration makes a very satisfactory as well as inexpensive illuminating device. The total cost is less than two dollars. What it lacks in appearance is more than made up in efficiency, for regardless of the orientation of the specimen on the stage it is always equally illuminated from every side.

By this time you have a pretty good idea of the general nature of a m/m and its use. There is only one limiting feature as to size: the specimen must be small enough to go into the mounting box. Other than that the size is determined only by what is intended to be shown. The limit at the other extreme is that the piece be large enough to handle with the finest tweezers. To show more than one crystal or feature of a group it may be necessary to keep the size of the specimen almost equal to the opening in the box. Very often on the same matrix there may be several crystals, each one showing a particular feature not seen in any other. To reduce the size further might render it less desirable for one reason or another. A specimen having a diameter of two mm. is about the smallest that can be mounted. Photographed to fill as much of a 35 mm. frame as possible without distortion such a specimen will be enlarged about 320,000 times when projected on a 5-foot screen. Consequently there is a great amount of detail seen, some of which is visible only with difficulty under the microscope and not even suspected when the specimen is examined with a 15x pocket lens. It is not difficult to determine what constitutes a good micro specimen; it may be an isolated crystal or a group of crystals or even a cleavage face.

The m/m has its beginning in the field where it is discovered first. It bears little resemblance to what it will turn out to be when properly mounted. More often than not the initial steps are long and tedious, perhaps ending in disappointment. It is wise not to attempt too much of this scaling down process in the field. Time and study spent in determining the best way to proceed are a good investment. If you have ever ruined a good cabinet specimen by a blow too heavy or from the wrong direction, you can appreciate how much more disastrous such a mistake can be when dealing with a small fragment intended for a micro specimen. It is better to take home a large piece which can be worked on slowly than to rush through with it in the field and lose the precious micro specimen. By trial and experience, which is just another way of saying by trial and disappointment, you will learn something of the breaking characteristics of different types of rocks. By learning the hard way you will understand why no set of rules can be given for trimming rocks.

On a field trip as a member of a group the easiest way to find thumbnail and micro mount material is to fall in behind the rest and search where they have been getting out specimens but moved on. It's a lazy way perhaps but generally very productive and the rejected material may prove ideal for your purposes. You may not believe it until you have tried, but there are no more favorable spots than an old quarry waste pile or a mine dump, especially a mine dump which does not represent deep workings. In either case you will be searching through deep material which has been exposed for perhaps many years. Rocks will be encased and caked with mud which will require washing and scraping to get down to where there may be something of value. Patience will be rewarded even if your find amounts to no more than two or three specimens to show for a day's work.

In addition to the material you may collect in the field it is always possible to find something in any dealer's stock. Surprisingly enough, some excellent m/m material will be found among the cheapest specimens. This is not always the case but the possibility should lead you to consider the cheap specimens. The investment is not great; not much is lost if most of it is discarded but you get one good specimen. Likewise if you buy a cabinet specimen it is possible very often to find a corner which can be removed without damaging the whole specimen. In that way you get a m/m as a bonus.

Perhaps the most important thing to learn about trimming is that a blow from your pick too heavy or in the wrong spot may cause a slender crystal to snap off and disappear. Such a detached crystal is more apt to be lost in the field than at home. If you think a crystal may be popped off, cover it with a handkerchief, tissue, or something of the sort. Then if a crystal does become detached it will be recovered probably. Assume that either in the field or at home you have reduced a large piece of rock to something like two or three inches in diameter. If the rock is tough and not brittle the task of further reduction is more difficult. A bedded structure or planes of cleavage simplify the problem. Whatever the characteristic of the rock the most use-ful and flexible tool for the final stages is a sturdy bench vise with jaws about three inches wide, capable of being opened up to five inches. As accessories you should have one or more of the detachable drill bits such as are in general use about most mines. The chisel type, V-shaped, is most useful, because it helps direct the break. The socalled cross bit can be very handy if one surface of the specimen is unusually rough, because of its gripping qualtity rather than its ability to give direction to a break. The vise may be used to break specimens either with or with-out these aids, as you will discover for yourself. To hold a specimen and one or two bits with one hand between the jaws of a vise while you tighten up with the other may sound quite complicated but it is done easily. Sometimes you may reach a point where it seems the pressure is not going to accomplish anything. Just wait, be patient; without warning the rock will rupture, surely if you give the vise jaw a few taps. If there is not room enough to get your hand under the specimen as it is in the vise to catch the pieces, wrap a piece of cloth around from the bottom, bringing the loose ends together over the specimen. It should be borne in mind at all times that much care should be exercised to prevent damage to what you hope will make a wonderful micro specimen.

For the final stages you will use just about anything which you think will do the job best. Nippers, cutting pliers, a light jeweler's hammer, or even homemade break-ers as illustrated, made out of ordinary "C" clamps, which are very inexpensive, as well as other tools will suggest themselves. The small carborundum discs which every dental technician uses, mounted in a portable electric drill are very useful though they must be used with care because it is necessary to keep them in line or they will snap.

Having reduced the specimen to the proper size it may be necessary to give some attention to the bottom side because of its irregularity. Grinding on a power wheel is fast but not always safe because of vibration. It is better to rub down the high spots on a piece of carborundum cloth. If the material is very hard an even surface may be obtained by applying a little plastic wood which must be allowed to dry thoroughly before proceeding. You are now ready to mount the specimen. The earliest boxes were made of paper blackened on the inside. The specimens were mounted on small corks affixed to the bottom of the box. The cork was blackened also. Most micro mounters carved out the top of the cork to accommodate the irregular under surface. A suitable cement, such as is used by model builders, is suitable for attaching the specimen to the mount. Common glue is not satisfactory because in time it may deteriorate, allowing the specimen to fall off.

The first step in mounting may be done in one of two ways. You may cement the support to the bottom of the box, then add the specimen after the support is firmly anchored. Some prefer to mount the specimen on the support first, then set the assembly into place. For handling the specimen as well as the mount a pair of thin curved-nose tweezers are preferred. The curved points enable you to grasp the support and hold it in a vertical position while placing it in the box. With straight pointed tweezers it is a little more difficult to manipulate in the restricted space of the box.

The writer prefers balsa wood for supports rather than cork, principally because the specimen can be mounted securely without showing underneath it a large area of the support. Balsa wood in strips of various diameters can be bought for a few cents in any model shop. These are painted dull black in the strip and cut into lengths as needed.

It is presumed that every collector will keep some sort of a catalog of his specimens. If up to the time of mounting the specimen has not been identified, the locality and date are the most important items. Every fact of environment, mineral associations, and geological setting will be of very great value later, especially if the material happens to be a species previously unidentified. All pertinent data so kept will enable you to establish your claims as original discoverer.

A simple way to describe the position of any crystal or other feature on a specimen is to mark the box so that it can be set in the same position always; a dot on the front of the box or on one side, just any distinguishing guide to uniform placement on the microscope stage.

Very often the most important feature of the specimen may be something that is not too easily seen at a glance, but if it is described as being in the center, the upper or lower right or left much time will be saved locating it in the field.

As has been pointed out, the principal piece of equipment for the micro mounter is some type of microscope of not too high magnification. There are a few accessories useful enough to be worth mentioning. A good bench vise and detachable bits have been mentioned, but as you progress with your hobby you will develop your own technique which will serve you better than trying to follow some pattern which you may not find wholly adaptable. Two pieces of soft leather, cut round or any convenient shape and stitched together around the edges, filled with very fine shot or sand makes an excellent pad on which to rest the specimen while working on it with dental tools. The rock will be cushioned and anchored, not apt to slip. In removing a single crystal using the probe as a sort of chisel it is best not to place the point too close to the base of the crystal; try to work on the matrix rather than on the crystal itself. You may press down with your hand or perhaps give the top of the probe a few very light blows; several light blows are safer than one heavy one. As a matter of fact the whole process from the collecting of the specimen in the field to the final step in mounting is like working with any other hobby; you visualize the end from the beginning and proceed to work it out your own way.

If you happen to be a collector of T/ns as well as m/ms you can do no better than keep your m/ms in the same type standard box. If you use the plastic boxes leave the dividers in place. The old style paper boxes, because of the extra thickness of the slip-on lid, would not fit into the regular spaces, but if the spacers or partitions are removed sixty-six paper boxes will go into one standard T/n box. For convenience, if you use the spacers and plastic boxes, something should be put into each compartment under the box. Otherwise it is difficult to grasp and lift out the box.

Arranging and numbering are matters of individual choice. If the mounts are numbered consecutively and kept in that order there is not much difficulty in finding any particular specimen. Numbers should be on the box rather than the lid. If you use the plastic boxes the number can be typed on a small piece of paper and inserted between the black paper filler and the box; it will be well protected there and unlikely to get lost. Some collectors use adhesive labels of the easily removable type on the outside of the lid or cover, which is all right if covers are not interchanged by accident. If specimens are numbered consecutively as mounted, a further aid to locating specimens quickly is to make out an ordinary 3 x 5 index card for each species and enter on it the numbers of the specimens of that species.

If the most economical utilization of limited space in your home is a necessity and you want to collect minerals the thumbnail size is recommended for a host of good reasons. If you wish to enjoy to the fullest extent the indescribable symmetry and matchless colors in minerals we recommend micro mounts. Finally, if you want to get the fullest enjoyment of the mineral kingdom combine the thumbnails and micro mounts. Even a small collection will afford many hours of real pleasure.

PHOTOGRAPHING MINERAL MICROMOUNTS

BY FLOYD R. GETSINGER Those who have seen the color slides of mineral micromounts projected on the screen often ask, “Did you use a portrait attachment?” or “Did you use a telephoto lens?” These are good questions, but actually the standard 50 mm. lens found on most 35 mm. cameras is the lens that is used, and you do not even need a shutter. We feel that from a practical standpoint the single lens reflex cameras are the best for this purpose. Other cameras, such as the Leica, are excellent provided they are equipped with a reflex housing. Any camera that is fitted with a sliding back for 35mm film so that focusing can be done on a ground glass may be used. A good example of the latter is the back that was made for the Recomar cameras a few years ago. This is the type that we did our first slides with.

Since our own equipment is strictly from hunger it is mostly home made with our own brand of accessories. The heart of the outfit is an Exa camera, and the only drawback to this camera is that it cuts down as much as 25% of the picture area on the 10X or 12X enlargements. All of the exposures in this type of work are made on “time,” so the speed and quality of the shutter is not important, nor is a “fast” lens necessary. All of the exposures should be made using one diaphragm stop only. We use f 22. The 2" Zeiss Tessar lens that came with the Exa is used for most of our work, although we sometimes use a 4" Schneider Xenar and a 7" Goerz Dagor for the larger specimens. The latter lens is used for 24x34 or larger negatives. When making direct enlargements on slides the thing to remember is that you need lots of bellows extension, (or lens extension tubes). The rule is to take the number of diameters you wish to enlarge, add 1 and multiply by the focal length of the lens you are using. Thus a 5X enlargement would take a bellows (or distance from film to lens) of 5 plus 1, or 6 times the focal length. Since the standard lens for 35 mm. is 2 inches it would require a 12 inch distance from lens to film. Our outfit has a 26 inch capacity, so by applying the above rule we can make a 12X direct enlargement, which is about the practical limit for color pictures of this type, according to our experience. Since we have never seen a bellows attachment of anywhere near this length offered on the market, we took an old view camera, cut it down, built a bellows, and the result is shown in the illustration. For the average person who would want to attempt this type of photography, there are lens extension tube sets on the market that will permit up to two or three diameters enlargement. This is ample for most workers. For lights we use two focusing auto spotlights. 32 cp bulbs, operated from a 6 volt transformer are used in the spots. (An ordinary doorbell transformer will not do. A heavy duty transFor lights we use two focusing auto spotlights. 32 cp bulbs, operated from a 6 volt transformer are used in the spots. (An ordinary doorbell transformer will not do. A heavy duty transFormer is required.) The spots are focused to cover an area about % to ½ inch in diameter. For larger specimens a 100 watt and a 200 watt “baby spot” lights are used since the auto spots concentrate the light on too small an area.Focusing is done by moving the camera or the object to and fro rather than by using the usual focusing back or lens ring. The focusing back, or extension tubes are used to obtain the size enlargement desired and for approximate focus. All the literature on this subject that we have ever seen has said to move the camera outfit for this final focus. With our first outfit that weighed 12 lbs. this was a very awkward thing to do, but that is what the book said, so we did it. After some years of this, the thought hit us that it would be much easier to move the ½ ounce specimen. The result was the stage shown in the illustration. The center support of this stage is an old lantern slide projector focusing mount with about a one-inch travel and a fine feed. Now the final focusing is accomplished by moving this platform up or down. Centering the minerals in the frame is quite a problem when pinhead size specimens are being photographed. For example a movement of 1/100 of an inch of the specimen causes a shift of ½ inch on the film. To take care of this we made our stage so that it would work like the mechanical stages used by microscopists. The two feed screws shown in the illustration cause the top of the stage to move very smoothly and with micrometer action, either to right or left, or to or from the operator. A microscope mechanical stage could be adapted for this purpose. Our stage may also be rotated. Of course provision must be made to move the camera outfit up or down to control enlargement size and rough focusing.

An exposure meter, although indispensable for ordinary color work is of very little value in photographing micromounts. (For cabinet size or larger specimens the meter is a good guide but don't forget to correct for lens extension.) Our exposures are all based on trial and error plus special factors (mentioned later) and past experience. Exposures have to be increased according to the distance between the lens and film. The rule for this is to square the distance between the lens and the film and divide by the square of the focal length of the lens. For example a 4X enlargement would require a 10 inch bellows draw (film to lens distance) for a 2 inch lens. 10 squared is 100. 2 squared is 4. 100 divided by 4 is 25. Therefore the exposure factor for this illustration is 25 times the normal or base exposure. All other factors, such as the introduction of color correction filters, must be added to this extension factor to arrive at the final exposure. To save time we made up the scales shown in the illustrations. By placing the zero end even with the film and reading opposite the center of the lensThe factor for extension is obtained. Readings are taken to the nearest ½ inch and interpolated if between full inch markings. Before making the exposure other things such as the color of the specimen and its reflecting power must be taken into consideration. The calculated exposure is then adjusted according to the judgment of the operator and is based more on "feeling" obtained through practice. A white crystal for example would take one half the calculated time while a black one would take from two to three times the calculated time. Since different equipment and lights will vary so much each person will have to determine his own base exposure. A series of "bracket" tests will have to be run, and perhaps a second or third series to determine this base. For what it is worth, our base is ½ second at f 22, ASA film speed of 8, using the auto spot lights described above.

We expect to have to expose each specimen an average of twice to get a good slide. A few will come out good on the first try, many will have to be shot a second time, usually with a color correction filter to get better color fidelity, while a few will have to be taken three or more times to get best results. (The color correction filters are placed between the light and the specimen, thus changing the color of the light. They are NOT used over the lens.) Our "pet" was taken about 50 times before we got one with correct color.

Because so much depends on trial and error, an accurate record must be kept on every exposure made, and the results noted. For this we keep record sheets headed as follows: Specimen No., Lens (focal length), Inches Extension, Diameter Enlargement, Filters, Base (exposure), Factors, Calculated Time, Actual Exposure, Color (of specimen), Remarks. Mostly, the remarks are filled in after the film is developed and consist of instructions for the next attempt. An actual example from our records follows: "Use CC 24 & CC 45, increase time a little." (CC 24 & 45 refer to color correction filter numbers.) In addition we have a line at the top of the sheet for Date, Film, ASA Speed, Lights, and other general information. Our first attempts were made with a daylight type film which is processed by the manufacturer. The reason for this was that we felt that there would be less variance in the color temperature of the light if we worked at about the same time of day every time and also that this would be the best source of light strong enough to take care of the large exposure factors involved. (Incidentally, a color temperature meter is an asset during the trial period.) Since we were not looking for pretty pictures but accurate color, the results of this test were most disappointing. Browns came out purple, greens were blue and a grey-brown came out dirty green. Only the yellow-orange of wulfenite was close enough to use. Our second test was made with artificial light using the special 3200 K photoflood bulbs, but the results were just as bad, the colors showing about the same variance as with the daylight film. This almost ended our mineral taking experience, but one day almost a year later we were beefing to a friend whose work requires many color photographs of artifacts, and he said he had had the same experience until he tried Ansco Color film, PROCESSING THE FILM HIMSELF! We tried this and got good results on everything except certain blue-green minerals like dioptase. The only trouble was that we made the mistake of using dioptase for our early tests, and that was the specimen mentioned above that required 50 shots to get a good one. However, in one of our early tests we used every color we could find in the micromount box, and the results were very good on all the other colors. On the dioptase we used every filter combination we could think of, built a special camera to try another type and brand of film, and even assembled a spectroscope to study the light reflected from the mineral. We wrote letters to the manufacturers of color film, talked to those working and experimenting with color film, and although we were getting closer, it was not until the Ansco Company brought out their new Anscochrome film that we got satisfactory results, and with that film we have had no trouble to speak of.

We want to point out that our friend recommended processing the film ourselves. That, we think, is important to those who wish to get best results in this type of work. Processing is not difficult although it is time consuming. We use Nikor reels and for developing tanks use 6 1-quart size polyethelyne fruit juice containers like you use in your refrigerator. Anyone familiar with ordinary film developing will have no trouble. The beginner can do it with a little practice, but there are a few things we would like to emphasize . . . Follow the directions in the developing kits and color manuals exactly. Control temperatures to plus or minus ½ degree or less. (We use a small bucket of ice and water connected to a water jacket which surrounds the various solutions. The ice water is admitted to the jacket through a home made thermostatically controlled valve which keeps the temperature within the limits. The thermostat is a 39e incubator control unit.) Mix developer fresh and do not use it if it is more than three or four days old regardless of what the directions may say about the keeping qualities, and do not overwork your developer. Better throw the developer away at 75% of rated capacity if you want the best results. There are so many variables in this work that they must be cut to a minimum. Always use the same lights at the same distance, the same diaphragm stop, same lens, developing technique, and vary only the specimen and the size of enlargement.

While our best results have been obtained with Ansco film, other workers may get their best results with other brands. Always stick to the film that gets the results you want, and don't switch from one to the other.

We use an automatic timer, connected to the lights to make all exposures. Since the slightest vibration will spoil the picture, the timer is placed on an adjacent table. The timer is set for the desired exposure then the camera shutter opened on time, with the lights off. After a few seconds to allow the camera to settle from any movement that may have been caused by opening the shutter the timer is set off. As soon as the taking lights have gone off, the shutter is closed, film advanced, etc. Room lights will have no effect on the exposure if this procedure is followed. Very few exposures will be as short as a second, and since our timer works from 1 to 55 seconds, we have all the range we need, except for a few maximum diameter enlargements. For those we set the timer to half the exposure and hit it twice. Exposures of more than two minutes get you into more technical difficulties, so it is better to cut down on the size of the enlargement than to try to increase exposures. On the long exposures you will probably find that the calculated exposure is too short, due to the failure of the reciprocity law, and longer times will have to be given. It is estimated that there are over 3 million "rock hounds" in the U.S.A. and many thousands of them have 35 mm. or other camera equipment that could be used for taking color slides. We hope that this outline of our experiences will be of some help to them and will get them started taking color pictures of their own interesting specimens. Except for the long extensions and high exposure factors, the same instructions will apply to cabinet or miniature collections, so dust off the old camera and have fun.