Kitabı oku: «Birds and Nature, Vol. 12 No. 5 [December 1902]», sayfa 3

The ruby is usually cut in the form of the brilliant, like the diamond, but sometimes the step cut is advantageously employed. The stones from India are usually rounded by the native gem cutters and worn in this manner.

Blue precious Corundum or sapphire is more abundant than the red or ruby. Like the red the blue color seems to be due to a content of chromium, since in the artificial crystals already mentioned as produced by Fremy, both colors occur at times in the same crystal. The blue color, however, unlike the reds, disappears on heating.

Blue Corundum exhibits various shades from light to dark, the color most highly prized being that known as cornflower blue. A good sapphire should also have high luster and a velvety sheen. As already noted, sapphire is somewhat harder than ruby, and it is also somewhat heavier. The Montana sapphires are said to be especially hard.

Sapphires have at the present time not over half the value of a ruby of the same size. A price of forty dollars per carat is an average one for a stone of not over ten carats and, as much larger stones are comparatively common, the price does not increase so rapidly as does that of the ruby with an increase in size.

The world’s supply of sapphires comes chiefly from Siam. The most important mines of that country are those of Battambong, a city southeast of Bangkok. The sapphires occur in a sandy clay out of which they are washed. The sapphire-bearing region is about a hundred miles in length. Together with the sapphires occur some rubies, especially in the southern part of the district. Sapphires also occur among the rubies of Burmah, but in small numbers. The so-called gem gravels of Ceylon furnish many sapphires, though their quality is not equal to those of Siam because of paleness of color. In these gem gravels occur also ruby, spinel, garnet, topaz, amethyst, tourmaline and hyacinth. Another locality for sapphires, discovered in the early eighties, is Banskar, in Cashmere, India. These stones were first disclosed by the fall of an avalanche, and later were discovered to exist in the region in considerable numbers. For a time they could be cheaply purchased, but are now jealously guarded by the government. The Montana sapphires have been known since 1865, but were not systematically worked until 1891. They occur in river sands east of Helena, and were first obtained in washing for gold. Now the mother rock has been discovered, and this is mined, the rock being taken out, piled in heaps and submitted to the action of frost through the winter. The sapphires thus become loosened and can be readily separated. These sapphires are well crystallized and are of good average size, though few gems exceed six carats in weight. Their luster and color are for the most part of first quality, and the stones are in demand for the best of jewelry.

Noble Corundum of other colors than those of blue and red is not of abundant occurrence nor is it ordinarily as highly prized as are the sapphire and ruby. Colorless sapphire or leucosapphire is sometimes used as a substitute for the diamond, from which it can readily be distinguished by its lower hardness and higher specific gravity.

Certain specimens of both sapphire and ruby, but especially the former, exhibit when lighted a six-rayed star. This appears as beams of light, radiating from a center, which changes in position as the stone is turned. Such stones are called star or asteriated sapphires or rubies, and are highly prized. They are usually cut with rounded surface, as this best brings out the figure. The cause of the star-shaped figure is generally supposed to be the presence of countless microscopic cavities in the stone, which are arranged parallel to the faces of a six-sided prism. The total reflection of the light from these causes the star. Others think that multitudes of twining lamellæ cause the appearance.

Sapphire is a word which is the same in nearly all languages. In Chaldean, Hebrew, Greek and Latin it has the same form as in modern tongues. This fact testifies to the ancient use of the stone. In early times sapphire was believed to be a destroyer of poison, so that if put into a glass with a spider or venomous reptile it would kill it. It was regarded also as a remedy against fevers.

SPINEL

The group of Spinel includes in mineralogy a number of species of different though analogous composition. The Spinel employed as a gem is almost wholly confined to the magnesium aluminate, having the percentage composition alumina 71.8 and magnesia 28.2. This is usually of a red color, different shades giving gems known by different names as follows: Deep red, spinel-ruby; rose-red, Balas ruby; yellow- or orange-red, rubicelle; violet red, almandine ruby. Spinel is thus known among gems chiefly as a relative of the ruby, and this sort of Spinel will first be considered.

The Spinel rubies differ from the true or corundum rubies in hardness, specific gravity and system of crystallization. The hardness of Spinel is 8, or about that of topaz, and the specific gravity 3.6. It is thus neither as hard nor as heavy as corundum ruby. Again, the system of crystallization differs. Spinel crystallizes in the isometric system and is usually found in the form, of octahedrons, while corundum ruby is hexagonal in crystallization. (See colored plate in November number.) Spinel is singly refracting in polarized light and corundum doubly refracting. Spinel ruby is infusible before the blowpipe, but on heating undergoes a curious series of changes in color which are quite characteristic. The red changes first to brown, and then becomes black and opaque, but on cooling the black changes to green, then becomes nearly colorless and finally the stone resumes its original red color. As a small percentage of chromium is usually found by analysis to exist in ruby Spinel, its color is generally considered to be due to this ingredient. While the Spinel ruby is considered of less value than the corundum ruby and is sometimes by fraud or error substituted for the latter, it yet has a definite value as a gem and is sold under the name of Spinel ruby or some of its varieties. This value is usually reckoned at about half that of the corundum ruby, although variations in quality of the stones, as well as changes in demand, cause differences of price. Thus Emanuel mentions a Spinel ruby of good quality weighing 40 carats, which in 1856 was sold for two thousand dollars, but which in 1862 brought at public auction only four hundred dollars. In 1866, however, it was again sold for twelve hundred dollars. The Spinel ruby of the French crown jewels, weighing 56 carats, was in 1791 valued at ten thousand dollars.

Not only is Spinel ruby related to corundum ruby in color and use, but the two are frequently associated together in nature. The gem gravels of Ceylon, Siam, Australia and Brazil contain both kinds of rubies, and the ruby mines of Upper Burmah, where the corundum ruby occurs in a crystalline limestone, produce also large quantities of Spinel rubies. Spinel rubies also come in large quantity from Badakschan, in Afghanistan, near the river Oxus, the name of Balas rubies, by which they are often known, being said to be derived from Beloochistan, or Balakschan. The Persians have a tradition regarding these mines that they were disclosed by an earthquake which rent the mountain in twain. The localities above mentioned furnish nearly all the Spinel rubies of commerce. A few have been found in North America at Hamburgh, New Jersey, and San Luis Obispo, California. But these localities have never afforded any appreciable supply. No Spinel rubies of great size are known. Bauer mentions as the largest known, two cut stones, one of 81 carats and the other 72½ carats, exhibited at the London Exposition of 1862. The King of Oude is said at one time to have possessed a Spinel ruby the size of a pigeon’s egg.

Spinel occurs in many other colors besides red, such as orange, green, blue and indigo, as well as white and black. Occasionally colorless Spinels occur, and as they cannot be distinguished by their behavior in polarized light from the diamond, it is sometimes sought to substitute them for the latter. They can be detected at once, however, by their inferior hardness. While Spinels of any color, if transparent and free from flaws, make desirable gems, the only colors found in sufficient quantity outside of the red to make an appreciable supply are the blue and the black. The blue Spinels resemble the sapphire in color, though they are somewhat paler. They come chiefly from Ceylon and Burmah, where they occur together with the ruby Spinel. The black Spinel is known as Ceylonite, or pleonaste, and is also obtained chiefly from Ceylon, although occurring of quality suitable for cutting at Mount Vesuvius in Italy.

Like the ruby, Spinel can be made artificially, the process being to heat a mixture of alumina and magnesia with boracic acid, and if the red color is desired, a little chromium oxide.

The Spinel ruby seems to have been known to the ancients equally with the corundum ruby, and the two were probably often confounded. The natives of India call the Spinel the pomegranate ruby and believe to this day that it possesses valuable medicinal properties.

Oliver Cummings Farrington.

THE WHITE-CROWNED SPARROW
(Zonotrichia leucophrys.)

 
With the snowflakes o’er the mountains
Hasten past the hawks from Northland,
Speed along the titmice, juncos,
White-crowned Sparrows, wrens, and creepers,
Tiny kinglets, sweet-voiced bluebirds,
All in eager search for havens
Where the touch of winter kills not.
 

– Frank Bolles, “Birds in October.”

Mr. Ernest E. Thompson calls the White-crowned Sparrow an aristocrat of the sparrow family. One of the largest of the sparrows, its beautifully marked plumage and its dignified mien, as it stands on some exposed perch, immediately attracts the attention of an observer. Its range is extensive, covering the whole of the United States during its migrations, and in winter it passes further southward into the valley regions of Mexico. In the selection of a nesting site a pure and cool atmosphere seems a paramount consideration. The mountain regions of the western United States and the country lying north of the great lakes and eastward into Labrador seem to meet the requirements for the home building of these sweet dispositioned birds. Then its music is sweetest. During its migration, however, localities not favored with its home are often regaled “with selections of its melodies as it rests in thickets and hedgerows while slowly passing through our country on its northward pilgrimage.” From some high bush or other favorable perch the male will pour forth an almost unbroken song while its mate is setting. Often this song does not cease with the going down of the sun, and it has been heard as late as midnight. It is a “lively, agreeable song, fine and clear, and is frequently heard from a score or more of birds at the same time with a most pleasing effect.”

Its song, quite closely resembling that of its relative the white-throated sparrow, with which it quite frequently consorts during its migrations, yet the two songs are readily distinguishable. Mr. Thompson compares the songs. He says: “Its usual song is like the latter half of the white-throat’s familiar refrain, repeated a number of times with a peculiar, sad cadence and a clear, soft whistle that is characteristic of the group.” Dr. Coues, speaking of the two songs, says that the song of the White-crowned Sparrow is “a less enterprising vocal effort, of only five or six syllables, like pee, dee, de, de, de, the two first long drawn, rising, the rest hurried and lowering.” Transcribed into words, there are almost as many renderings of the White-crowned’s song as there are observers. Mr. Burroughs says that the song “begins with the words fe-u, fe-u, fe-u, and runs off into trills and quavers like the song sparrow’s, only much more touching.” To Mr. Langille “the song is quite peculiar, whee-who-who-zee-zee-zee, the first three notes in a clear whistle and the last three in a sort of jew’s-harp tone, the whole being decidedly pleasing, and not at all like that of the white-throat.”

The food of the White-crowned sparrow consists of both insects and seeds. To some extent they feed upon berries, and Audubon states that in Labrador they also eat minute shellfish, “for which they frequently search the margins of ponds or the seashore.” This bird is a scratcher. It is also a hopper and hence scratches with both feet at once.

The nest of this Sparrow is usually constructed of grass or moss and is placed either on the ground or in low bushes. Audubon describes a beautiful nest of this species which he found in Labrador. This nest “was placed in the moss, near the foot of a low fir, and was formed externally of beautiful dry green moss, matted in bunches, like the coarse hair of some quadruped; internally of very fine, dry grass, arranged with great neatness, to the thickness of nearly half an inch, with a full lining of delicate fibrous roots of a rich transparent color.”

Of this beautiful Sparrow Mr. Burroughs has said: “Among the birds that tarry briefly with us in the spring on their way to Canada and beyond, there is none that I behold with so much pleasure as the White-crowned Sparrow. I have an eye out for him all through April and the first week in May. He is the rarest and most beautiful of the sparrow kind. He is crowned as some hero or victor in the games. His sparrow color, of ashen gray and brown, is very clear and bright, and his form graceful. His whole expression, however, culminates in a regular manner in his crown. The various tints of the bird are brought to a focus here and intensified, the lighter ones becoming white and the deeper ones mainly black. There is the suggestion of a crest also, from a habit this bird has of slightly elevating this part of its plumage, as if to make more conspicuous its pretty markings.”