Fluorescent Minerals

Closely following each upward zoom of the magic carpet to new heights of scientific advancement is a train of new words. The discovery is named; there are words to describe its characteristics, its relation to the basic sciences-chemistry, physics or both-and a host of words more necessary to clarify and amplify the significance. Occasionally the lay public is introduced to such new terms almost immediately, especially if the discovery pertains to every-day life. Thereupon a few readily understandable terms quickly become permanent additions to our vocabularies. On the other hand, the discovery may be made, described with scientific accuracy and catalogued, but because no immediate application appears the most of us hear little about it and the facts are tucked away in the archives holding other records of scientific progress, and for a time almost forgotten. Such a word is fluorescence Fluorescence was coined in 1852, after Sir G. G. Stokes had further investigated a peculiar phonemon discovered twenty years earlier by Sir David Brewster. Brewster called it "internal dispersion." Stokes substituted fluorescence as a more convenient term, derived from fluorspar, without presupposing any theory, but following the analogy of opalescence from opal. However, some fluorspar will fluoresce and some will phosphoresce if heated gently. To be accurate historically we should credit a cobbler of Bologna, an alchemist in spare time, with the discovery of this phenomenon. He found that barium sulphide glowed when he heated it in an attempt to distill precious metals from it.

For nearly one hundred years fluorescence was known only to physicists. It was not until quite recently that the same capacity to emit light was discovered in many minerals and subsequently in organic substances as well that the word came out of hiding. Studies of the phenomenon of fluorescence, including ways to promote it, have progressed rapidly since then. As the list of fluorescing minerals increased the word naturally became a part of the current vocabulary of every mineral collector. Following the perfection of fluorescent lamps for various types of illumination the term has become widely known and used by almost everyone.

The scientist calls this emision of light luminescence, subdividing it into several categories according to the energy which produces it. The more common subdivisions are: thermo-luminescence, tribo-luminescence, photo-luminescence and cathode-luminescence. Thermo-luminescence is that produced by the application of heat as in the case of fluorite or steel heated in a forge. Tribo-luminescene is produced when a mineral is rubbed or scratched or two pieces are rubbed gently together. Photo-luminescence, most commonly observed and most easily produced, is again sub-divided into fluorescence and phosphorescence, the phenomena which make those carefully arranged displays of the mineral collector a riot of vivid colors, a source of wonderment and admiration especially to his uninitiated guests. Phosphorescence differs from fluorescence in that the glow continues for a longer or a shorter period after the activating force is removed.

What are those activating forces and how can we manage them? Stated simply the exciting energy is an invisible emanation from an ultra-violet source, which, absorbed by the material, alters the wave length causing the fluorescent substance to emit energy in the form of visible light. There are several ways of creating the necessary energy. Some require rather expensive and cumbersome apparatus. Others are easily handled and relatively inexpensive. The most convenient and satisfactory sources are the ultra-violet lamps, made in a wide variety of sizes, portable for field use and others for home use to be operated on the usual 110 volt A.C.. house lighting circuit. Ultra-violet light is generated in a tube of pure fused quartz by passing an electrical discharge through mercury vapor. Pure fused quartz is the only material which will transmit 100% of the ultra-violet light. Since there is a small amount of visible light in the ultra-violet light so generated a filter of special glass is placed over the quartz tube to screen out as much visible light as possible. The sun is a natural source of ultra-violet light but due to the variable conditions of the atmosphere through which these rays must pass, by the time they reach us there is not sufficient intensity to be useful for observing fluorescence.

For the beginner in fluorescent minerals a bit of caution is pertinent. There are more than one hundred minerals which will fluoresce but there are differences in the color of the light emitted by a given species. It is also true that different sources of ultra-violet light or different kinds of filters may produce different colors in the same specimen, so beware of snap judgement based on fluorescence. Fluorescence is not a positive means of identification for any mineral. For example calcite tested from more than twenty-five widely separated localities show no less than seven distinct colors, which could be sub-divided by shades into more than twice that number. The one mineral in which there is the least variation in color is scheelite, a calcium tungstate, a highly important source of the alloy metal tungsten. For this reason the ultra-violet lamp is a valuable tool in the prospecting for tungsten.

So much for the scientific aspects of this interesting phenomenon. Now let us think about fluorescence at home. The mountains, the valleys and vast desert plains abound with minerals. To the uninitiated they may be only "pretty stones."

FLOURESCENT MINERALS

To the mineralogist they are of considerable interest. Some species are common; others are found only after long and diligent search. Of the nearly three hundred mineral species identified in Arizona more than twenty-five varieties fall within the fluorescent group.

One of the most fascinating characteristics of fluorescent minerals is the fact that in ordinary or visible light, be it daylight or artificial light, most of them appear quite drab and unattractive. When touched by the magic ultra-violet rays the transformation is immediate, startling and almost unbelievable. It is an especially impressive experience on the desert on a moonless night if you are equipped with one of the several types of portable lamps. The soft, bright glow of emitted light from a fluorescent object is a little spookish. Stooping over to examine one of these glowing spots you may flush a scorpion which will fluoresce vividly as long as he is in range of the ultra-violet rays.

The questions most frequently asked are: where do such minerals occur, what are they and which are the most abundant. To the first question we can reply that they may occur anywhere on the pebble strewn desert, in the rock exposures in mountains and abundantly in some mines. You may suspect their presence but cannot prove it without some source of ultra-violet energy at your command. The following fluorescent minerals have been found in Arizona. Agate, Apatite, Calcite, Chalcedony, Cinnabar, Erythrite, Fluorite, Hyalite, Hydrozincite, Mercury, Meta-torbernite, Mexican Onyx, Opal, Opalite, Opalized Wood, Petrified Wood, Powellite, Scheelite, Selenite, Sphalerite, Torbernite, Vanadinite, Uranium minerals not classified, Willemite, Wulfenite and Wurtzite. Cinnabar and Mercury do not fluoresce but the presence of mercury can be detected as described later. Not every specimen of any species will fluoresce, a fact not satisfactorily explained as yet.

It is not quite so easy to decide which are the most abundant. In a measure this depends upon the locality. On the desert and in or close to washes which drain an area of younger volcanic rocks in which silica has been deposited in the form of agate or chalcedony fluorescing material is abundant. It is quickly seen at night because of the soft yellowgreen glow. In the specimen (especially in the "desert roses") the fluorescence may not be evenly distributed but inclined to be in spots, or in bands. It is believed that this color is due to small amounts of uranium. Agate and "desert roses' not yet released by erosion but still embedded in the rock will glow when flashed with the light.

In mines and to a lesser degree in certain desert areas calcite is often very abundant. Unfortunately not all calcite will fluoresce. The characteristic color is red. Sometimes it is very intense, like glowing coals. Many pounds of such material from an Arizona locality, advertised as "Coals of Fire" have found their way into collections all over the country. From intense red the color grades off to a delicate shell pink. In a few localities the calcite may fluoresce blue, green or yellow, in pale shades but the characteristic color is a shade of red. A rare calcite from Bagdad will fluoresce blue. From Bisbee comes another unusual variety which seems to be coated with a soft, easily removed pulverent material of a green color. Such specimens show two colors of fluorescence. With the filter in place the calcite (where not coated) shows a beautiful deep red. With the filter removed the green coating shows a rich dark green and the brilliant red in spots.

We have mentioned the important mineral scheelite. Ordinarily it is quite inconspicuous. In color it ranges from

Continued from page thirty

water-clear white, through gray or light cream to rather dark tan. If it occurs in distinct crystals or in pieces large enough to be "hefted" (it has a high specific gravity, hence heavy) its identification is not so difficult. When it occurs disseminated through rock masses in grains from a quarter of an inch in diameter down to mere specks of microscopic size its presence may not be suspected unless there is enough of it to give the rock an unusually heavy feel. The ultra-violet rays reveal even the very minute particles as brilliant blue-white spots. Few minerals show a fluorescence which might be mistaken for scheelite and in most cases simple field tests serve to make the determination positive.

Powellite, closely related to scheelite in composition and frequently mistaken for scheelite is moderately abundant in Arizona. It is a double salt of calcium molybdate and calcium tungstate. When the amount of calcium tungstate does not exceed the amount of calcium molybdate the mineral is classified as powellite. As the molybdenum content increases the characteristic bright blue fluorescence of scheelite softens through pale blue to white then cream which deepens to yellow when more than 50% calcium molybdate is present. Some flakes of molybdenite, a sulphide of molybdenum also quite abundant, are coated with a thin film of powellite.

There is a general impression that all uranium bearing minerals should fluoresce. As a matter of fact very few of them do. So far only one identified uranium bearing mineral in Arizona will react to the ultra-violet light. That is the meta-torbernite, found first at the Castle Dome mine but since discovered elsewhere in the state. The search for uranium minerals in Arizona has presented some perplexing problems. Material which will register a moderate amount of uranium content when tested with a Geiger counter may or may not fluoresce in spots. The gangue matter in either case, to all outward appearances, is the same but in one case brilliant green areas, resembling torbernite are seen while in another apparently identical specimen there is no fluorescence. Both specimens, by analysis, have the same uranium content. The fluorescing material is as yet unidentified because it occurs in such minute particles that it cannot be isolated.

In mines the display may not be quite as eerie as on the open desert where the silica minerals show their wierd emanations but is often more spectacular, especially if much fluorescing calcite is present. Three zinc minerals, willemite, a silicate, sphalerite a sulphide with variable amounts of iron, and hydrozincite, a basic zinc carbonate all fluoresce. Willemite and calcite frequently occur together the former fluorescing a brilliant green, the latter deep red. The dazzling blue-white of hydrozincite, especially in large masses, is very spectacular. Ordinarily sphalerite does not fluoresce. A variety found recently in one of the deep mines in Arizona shows a gorgeous apricot color comparable to the much prized wernernite from Canada. Another Arizona sphalerite is triboluminescent; it will emit a streak of light when scratched lightly with the finger nail. A variety of "bull quartz" also exhibits tribo-luminesence when rubbed lightly with another piece of the same material. The reaction should be expected in all "bull quartz."

Vanadinite and wulfenite from one Arizona locality have been reported on very good authority to show a deep green fluorescence. Testing a few specimens from this mine failed to produce the reaction. This does not mean necessarily that the report cannot be confirmed. Such inconsistent reactions in minerals even from the same locality are not uncommon.

Spectacular progress is being made on gigantic Davis Dam.

This drawing by Reclamation Engineer J. MacGilchrist shows how Davis Dam and Power plant will look when completed. Dam, which is thirty miles from Kingman, will form a lake ideally situated for sportsmen. A modern highway will cross the dam.

BY NORMAN G. WALLACE

Far downstream from Boulder Dam, sometimes known as Hoover Dam, another dam is rising out of the depths of canyons along the Colorado River. Sixty-seven miles below Boulder Dam, on the Arizona side of the river there is an immense rock almost blocking the flow of the river, and the shape of this rock has given it the name of "Bulls Head Rock." Directly across from Bulls Head Rock there is another solid rock hill rising from the edge of the river for hundreds of feet. Just below these rock formations the Davis Dam is being built, under the direction of the Bureau of Reclamation, by a private contracting company.

The work on the Davis Dam has been under way for several years, but during the past year more spectacular progress has been made than at any previous period. One of the big jobs to accomplish in building such a large dam is to control the flow of the river so that the actual dam site may be prepared for the materials to be used in its construction. It was the building of the control features which has made the past years work show up so vividly.

The Davis Dam is to be of a rock and earth fill type. with its crest about 138 feet above the bed of the river, about 1600 feet long at the crest and causing the river to rise about 122 feet above the original surface of the water. It was necessary to carry the water around the dam site by means of a diversion channel through a solid rock hill on the Arizona side, where it was necessary to excavate to a depth of 200 feet to bring the entire flow of the Colorado river to the fore-bay channel and then to the spillway and power house. This last job has been accomplished recently and now the entire flow of the river goes down this man-made channel and will continue to do so from now on.

In addition to controlling the flow of the river, it was necessary to bring in from selected deposits of rock, earth and clay, the materials which will be put into the dam proper. It will take about sixteen million cubic yards of material altogether to build the dam and controlling works, including the immense cuts for the diversion channel. During the summer of 1948 the flow of the Colorado River was diverted around the dam site by means of large coffer dams, and a great amount of concrete work done, which included the building of the tall concrete pier in the middle of the diversion channel, the pier being needed to support the long 545 feet long bridge which will carry the new highway across the diversion channel and the crest of the dam after completion.

The elevation of the river surface before the work started was about 525 feet above sea level, and the dam will cause the water to rise to an elevation of 647 feet above the sea, so that the net increase in the level of the river amounts to 122 feet. The construction of the dam is so arranged that the core will be made of an impervious clay, with a great bank of rock screenings on each side of the core, and then there will be a tremendous blanket of heavy rock outside of these interior materials which will make the dam practically water tight. However there have been arrangements made to lay a cunning net work of small wire all through the dam structure which will automatically record the pressure inside of the dam at all times, from the bottom to above high water level.

The force of employes necessary to build such a large structure must, of course, be large, and their comfortable housing a necessity on account of the high temperatures during the summer months. The Bureau of Reclamation has built a neat town of its own on the Arizona side of the river about a mile below the dam, and the contractor's force has another town on the Nevada side of the river, both towns being readily reached from Kingman, Arizona, thirty miles away, or from California and Nevada on the west.

There is also a new town about three miles down river known as Bull Head City, where those who wish may reside. or carry on a small business. There is always good cat fishing along the river banks and even bass and trout fishing, as some of the trout put in the river at Willow Beach fifty miles up stream have found their way down to the dam site. The water is blue and cool and no longer does the muddy water flow as it did before Boulder Dam was built several years ago sixty seven miles upstream. The mud is out of the muddy river.

Work on Davis Dam is near the half-way mark. It is expected that the dam will be completed in 1950. The dam, of a rock and earth fill type, will further control the Colorado River and add to the power development of this most important stream. Left, general view of downstream section of diversion channel. Below, views of intake, spillway and outlet structures of dam.

This view is looking upstream from the edge of the deep rock cut that was made for the diversion channel. Bulls Head Rock is seen just above the temporary bride in right distance. Concrete pier on left is 165 feet high and will be in the middle of the new highway bridge, which will be 545 ft. long and about 166 ft. above the bottom of the excavated rock channel. Arizona is on right.

Davis Dam can be reached by highways both from the Nevada and the Arizona sides. Despite the fact that only in recent months has the dam begun to take shape, the place is already becoming a place of tourist interest. Davis Dam, Arizona, built by the Bureau of Reclamation, has been completed and will be the permanent government town for employees operating the dam and power house after construction. It is a model city. Bullhead, Arizona, has grown up since work started on the structure.

YUMA-CITY OF THE FUTURE Continued from page thirteen.

housewife has a choice of some forty food stores, one of them a member of the Safeway chain.

To go into individual food prices would require space that would probably find itself wasted for today's cost of butter might change between the coming of night and the dawn, and with an equal difference. Suffice to say that a basket of groceries, with a stop at the meat counter, will take as great a part of a $20 bill in Yuma as it takes in just about any other locale in the country.

As for the means used in coming by that $20 bill, the greater part of which was used a paragraph above, Yuma has need of just about any service except that offered by those who mine for coal.

That doesn't mean that you can load the family jalopy. get out the road map and head for Yuma expecting to find the fabled land of milk and honey upon reaching the city limits.

But it does mean that Yuma's unemployment problem isn't one that has her City Fathers sitting up nights worrying about how to feed former taxpayers.

If one were to write the book of Yuma the majority of its chapters would necessarily have the word agriculture in their titles. It is easy to understand this when one considers Yuma as the natural phenomena it is its land grows while the rest of the country grows and it also grows while the rest of the country rests for climatic reasons.

It must be understood that the city of Yuma doesn't pave its street with flax seed nor use its grapefruit trees as light standards. The three square mile area that is the city is the banker. the baker, the butcher and the candlestick maker to the 78,600 acres of crop producing land surrounding it. Within these boundaries are communities like Somerton, Wellton, Roll. Gadsden, and others, all thriving places with more than the American proverbial post office but all looking to the big brother county seat-Yuma-for the luxuries, the staples and the legal aspects of life.

To best understand the importance of agriculture in the Yuma area one must look at records attained and records broken in production of crops.

The average flax seed production for the United States is about ten bushels to the acre. In Yuma County the average for flax seed is over thirty bushels to the acre. And the higher oil content of Yuma flax seed heaps an extra twenty-five cents per bushel premium, adding polish to the fruits of victory.

The world's record for alfalfa seed production rests securely on the books of J. P. Ellington by virtue of 1,820 pounds to the acre on his place near Roll in the Mohawk Valley in 1942.

The U. S. average for barley is 25.5 bushels to the acre. Yuma County yields consistently hit the eighty bushel to the acre mark. Over 90% of the world's entire crop of Bermuda grass seed goes out to groups using it for erosion control, lawns, airport seeding and park planting with the boxes labeled "From Yuma County" and the per acre average production of grapefruit is higher in Yuma County than in any other desert region in the country.

Individual records do not always make the team score, however, so Yuma County is quick to point out that the amazing productivity of its land is not a spotty affair.

The proof of that lies not in the Chamber of Commerce office but in figures from the Southern Pacific railroad's bills of lading and the First National Bank of Arizona, Yuma.

In 1947 the gross income from Yuma County's 78,600 cultivated acres stood at $19,042,569.

But there's more to it than hay, flax, bermuda and barley. There's also wheat, oats, cotton, pecans, dates, citrus, cantaloupes, watermelons, carrots and lettuce. And all in quantity.

Also to be added to the 1947 land income figures is the gross income from 8,000 head of fat cattle and 14,000 fat lambs which were shipped to Yuma County for winter feeding. This made the total gross income per acre in Yuma County a cool $260.

Admittedly, 1947 was a good year for Yuma County agriculture. It was a good year for practically everything, everywhere in the income line.

But even in the low prices of 1935-39 the gross income per acre was $166.

But Yuma County has the distinction (enjoyed in few areas) of being able to quote existing high figures and scoffing. "You ain't seen nothin' yet."

She points with understandable pride to car loadings and shipping of 8,397.7 cars in 1939 and an increase to 17,317 in 1947. But she still asks that you look (with her) into the future.

She smiles a smile of accomplishment and well-being when she shows you figures of bank debits totaling $22,101,950.36 in 1935 and an increase of $128,934,106.42 in 1947. But she sports an even wider smile when she thinks of what those figures will be in the future.

Why the smiles, the figurative uplifted palm asking you to "wait and see what's coming?"

That is because of another set of figures, another comparison-78,600 acres in production in 1947, double. triple. (and perhaps even more) from 1950 to 1957.

Dreams? Hopes?

No. Congressional approval, Bureau of Reclamation green lights.

It was June 30, 1947 that The Yuma Daily Sun got out its largest type and headlined the news that Yumans had been waiting years to hear-GILA BILL PASSES.

Those three words told a story that would fill volumes, a story that included more heartbreak than can be heard in a month of radio soap operas, more devotion to purpose than can be read in a hundred classics on martyrdom, more "behind-the-scenes" political machinations than make up a presidential campaign.

But they were the final chapter in a fight that ran the course of decades and brought, with the victory, 115,000 acres of irrigable Gila Project land into the Yuma agricultural scheme of things.

The Gila Project comprises 40,000 acres of the Yuma Mesa division and 75,000 acres of the Wellton-Mohawk Division. The Yuma Mesa section is made up of 25,000 acres just south and east of Yuma with the remaining 15,000 acres lying in the North and South Gila Valleys. The WelltonMohawk begins twenty miles east of Yuma and runs approximately thirty miles eastward on both sides of the Gila River.

The potentialities of this land is well known. It's use has been disappointing in late years for the small portion of it that has been farmed received its water from wells, the salt content of which made profitable planting impossible. Tests have proven that with the introduction of Colorado River water production can reach the record breaking heights enjoyed in the river irrigated lands.

The Gila Bill authorization was the go-ahead needed for the look into the rosy future Yumans claim.

This new 115,000 acres only serves to increase the position held by Yuma itself. It is the largest community in the area. Next in size is Somerton, population 2,500, which is close to the southern end of the Yuma Mesa Division.

Wellton and Roll, each with less than 1,000 population. lie in the Wellton-Mohawk Division.

Yuma, therefore, can be likened to the hub of a half wheel with spokes extending southwest through Gadsden and Somerton, southeast through Wellton and northeast through Roll.

But the spokes extend even beyond these Yuma County communities. They push their relentless way through the irrigated soil across the international boundary and down into Mexico itself.

The seven million dollar Morelos Dam, scheduled for completion in 1950, will divert Colorado River water into the sluice gates and canals of Old Mexico and will mean that crops from additional thousands of acres will be funneled through the Yuma transportation hub to the markets of Central and Northern California, on to the great Northwest and. on again, to the seasonal markets of the East.

That is what the Yuman sees in the future, himself as the hub, steady with a fit economy, steady as a centering point for the spokes of growing, shipping and commerce that make the half-wheel of wealth.

The Yuman knows this, understands this and is willing to work to bring it about.

And he is willing to share it with others to come, the veteran whose capsuled name, drawn from the pickle jar, entitles him to a portion of the land in the new projects; the merchant who comes with his goods; the trucker who comes to haul; the butcher, the baker and, yes, the candlestick maker.

The Yuman knows his summers are hot, but he's getting air conditioning and has his coolers. The Yuman realizes that his city has grown too fast to allow for adequate street lighting, paved streets, sewers and entertainment facilities. But his city council is planning a $650,000 bond issue for a sewer project for the entire city. The Arizona Edison Co. has plans on paper for his street lights and more of his streets are being hard-surfaced every day. A city Recreation Commission has been appointed to provide his children with playgrounds and to plan for a civic auditorium so he will have a place in which to enjoy the entertainment he wants.

The Yuman knows his hotel facilities leave much to be desired. He has heard complaints from the few conventions he has been able to get to the effect that he is throwing away a chance for a multi-million dollar tourist trade through lack of adequate capital for building the pleasure palaces to utilize his greatest natural resource, the sun. But he knows that land has been purchased for two dude ranches and contracts are being let for deluxe motor hotels.

Yes, the Yuman has a "but" for every disadvantage.

In fact there is only one thing the Yuman will not tolerate, will not excuse.

It's best understood in the words of the old timers who remember when water was sold at so much per bucket.

"We want 'em all to come here, we want 'em all to make money and be happy. But we don't want a damn one of 'em who comes with his hand held out 'lessen it's a helpin' hand."