THE DIAMOND MINES OF SOUTH AFRICA *

HE famous diamond mines of South Africa are in the neighborhood of Kimberly, De Beers, Dutoitspan, and Wesselton. Kimberly is practically in the center of the present diamond-producing area. Besides these mines others of some importance in the Orange River Colony are known as Jaggersfontein and Koffyfontein, Lace, and Monastery, besides two new mines, the Roberts-Victor and the Voorspoed.

In 1907 the total number of carats raised from these mines was more than two million and a half, the sales of which realized over $30,000,000.

The most important mine outside the Kimberley group is the new Premier Mine, about 20 miles West-North-West of Pretoria, where the famous Cullinan diamond was found.

THE PIPES OR CRATERS

The five diamond mines or craters are all contained in a circle 32 miles in diameter. They are irregularly shaped round or oval pipes, extending vertically downwards to an unknown depth, retaining about the same diameter throughout. They are said to be volcanic necks, filled from below with a heterogeneous mixture of fragments of the surrounding rocks, and of older rocks such as granite, mingled and cemented with a bluish-colored, hard, clayey mass, in which famous blue clay the imbedded diamonds are hidden.

Besides diamonds, there have been detected more than eighty species of minerals in the blue ground. The blue ground does not show any signs of passing through great heat, as the fragments in the breccia are not fused at the edges. The eruptive force was probably steam or water-gas, acting under great pressure, but at no high temperature.

Before the discovery of the mines there was nothing in the superficial appearance of the ground to indicate the treasures below. Since the volcanic ducts were filled with the diamantiferous ground, denudation has planed the surface and the upper parts of the craters, and other ordinary signs of volcanic activity have been smoothed away. Other hoards of diamonds may also be near. Where there are no surface signs, and the pipe itself is hidden under 10 or 20 feet of recent deposits, it is impossible to prospect the entire country. Accident has hitherto been the chief factor in the discovery of diamond mines.

*Abstracted from Sir William Crookes' little book on "Diamonds" (1909), Harper and Brothers, New York. The book is one of "Harper's Library of Living Thought."

How the great pipes were originally formed is hard to say. They were certainly not burst through in the ordinary manner of volcanic eruption, since the surrounding and enclosing walls show no signs of igneous action, and are not shattered or broken up even when touching the "blue ground." It is pretty certain these pipes were filled from below after they were pierced and the diamonds were formed at some previous time and mixed with a mud volcano together with all kinds of debris eroded from the rocks through which it erupted.

KIMBERLEY MINES AT THE PRESENT DAY

The De Beers Consolidated Mines, Limited, was founded in 1888 mainly through the genius of the late Cecil John Rhodes, for the purpose of acquiring all-important diamond-mining interests in the Kimberley area and thereby controlling the output. The two richest mines, Kimberley and De Beers, have been actively worked ever since, and have been the main contributors to an output which now realizes over thirty million dollars annually. The success of the consolidation is proved by the fact that since it was brought about, $120,000,000 have been paid in dividends to the shareholders, and it is roughly estimated that 40,000,000 carats of diamonds have been produced, of a total value of over $400,000,000. (1908).

The Compound System.-With gems like diamonds, where so large an intrinsic value is concentrated into so small a bulk, it is not surprising that robbery has to be guarded against in the most elaborate manner. The illicit diamond buying (I. D. B.) laws are very stringent, and the searching, rendered easy by the "compounding" of the natives, is of the most drastic character. It is in fact very difficult for a native employee to steal diamonds.

The Depositing Floors. Owing to the refractory character of blue ground fresh from the mines, it has to be exposed to atmospheric influences before it will pulverize under the action of water and mechanical treatment.

The depositing floors are prepared by removing the bush and grass from a fairly level piece of ground; this ground is then rolled smooth and hard. The floors extend over many square miles of country and are surrounded by 7-foot barbed wire fences, vigilantly guarded day and night. The ground from the Kimberley Mine is the softest and only needs a few months' exposure on the floors; the ground from De Beers is much harder and requires at least six months' exposure, while some ground is so hard that it will not disintegrate by exposure to the weather under one or two years.

For a time the blue ground remains on the floors without undergoing much alteration. But soon the heat of the sun and moisture produce a wonderful effect. Large pieces, as hard as ordinary sandstone when taken from the mines, commence to crumble. At this stage the winning of the diamonds assumes more the nature of farming than mining. The ground is frequently

*This does not fully accord with the views of several geologists who consider that the diamonds are a part of the original volcanic material. Editor.

harrowed and occasionally watered, to assist pulverization by exposing the larger pieces to atmospheric influences. The length of time necessary for the ground to weather before it becomes sufficiently pulverized for washing depends on the season of the year and the amount of rain. The longer the ground remains exposed the better it is for washing.

Washing and Concentrating Machinery.-After the blue ground has been weathered for a sufficient time, it is again loaded into trucks and hauled to the crushing machinery. By crushing and washing most of the useless waste is taken out and the mixture of gravel and diamonds remains. From this mixture the rough diamonds must be sorted. For years this was done by hand. Later, after months of experimentation, an automatic sorting process. was discovered. The remarkable discovery was made that diamonds alone of all minerals contained in the blue ground will adhere to grease, and that all others will flow away as tailings over the end of the percussion table with the water. Now all the sorting (except for the very coarse size) is done by these machines, whose power of distinction is far superior to the keenest eye of the native.

The discrimination of this sorter is truly marvelous. Native workers, although experienced in the handling of diamonds, often pick out small crystals of zircon, or Dutch boart, by mistake, but the senseless machine is practically unerring.

VARIETIES OF DIAMONDS

Diamonds occur in all shades, from deep yellow to pure white and jet black, from deep brown to light cinnamon, also green, blue, pink, yellow, orange, and opaque.

The diamonds from each mine have a distinctive character, and so uniform are the characteristics that an experienced buyer can tell at once the locality of any particular parcel of stones.

Noteworthy Diamonds.-Prodigious diamonds are not so uncommon as is generally supposed. Diamonds weighing over an ounce (151.5 carats) are not infrequent at Kimberley. Some years ago, in one parcel of stones, I saw eight perfect ounce crystals, and one stone weighing 2 ounces. The largest diamond from the Kimberley mines weighed nearly 4 ounces troy. It measured one and seven-eighths inches through the longest axis and was 112 inches square. The diamond, called "Cullinan" was presented to King Edward on his birthday by the people of the Transvaal. It weighed no less. than 1.37 lb. avoirdupois. It was a fragment, probably less than half, of a distorted octahedral crystal; the other portions still await discovery by some fortunate miner.

We are requested by the North Star Woolen Mill Co., Minneapolis, to state that the educational exhibit furnished by them to schools has a nominal charge of 25 cents. They were erroneously referred to in the Sept., 1912, JOURNAL as the Lone Star Woolen Mill Co.

T

THE EMERALD MINES OF COLOMBIA

AHE best emeralds of the world come from the Republic of Colombia, in South America. The famous emerald of the Duke of Devonshire is a Colombian, as is also the equally famous stone in the Hope collection.

This source of emeralds was known almost immediately after the discovery of America, for the native peoples had used the stone in their own way in some cases considering them as precious, with a strong religious significance.

Colombia supplies by far the larger quantities of emeralds. The Government does not, however, admit this mining as an open industry, restricting the deposits in the country to Government control and monopoly. The chief areas in which emeralds are found are near Bogota, the capital of the Republic, Coscuez, being one, and the better known Muzo, another. At present the concession is held by an English company, which can work the mines for 20 years, but may not extract more than the value of $1,250,000 a year, as it is thought that by this means a depreciation in the market may be prevented.

As a mineral the emerald is a silicate, the combination being with oxides of aluminum and glucinum. Other stones have the same chemical combination, the difference in color being produced by varying proportions of the ingredients, and the value placed upon any one of them-emeralds as well-depending upon the intensity of color. Chemically the emerald has about 68 per cent of silica, 15 to 18 per cent of alumina, say 15 per cent of glucina, and small proportions of iron, lime, and chromium oxide. Much of the green depends upon the amount of chromium. The specific gravity is from 2.577 to 2.725, and its hardness is much less than that of the topaz.

A fine stone of 5 carats will cost about $5,000, but such an emerald is rare. Others of less brilliancy and weight are of course of less worth. The emeralds from Muzo are celebrated for their color and "water," their clear

ness.

The deposits are found in horizontal layers embedded in fossilized bituminous substance, and when first exposed to the air are relatively soft. They harden, however, as time goes on. There are several groups of deposits, all within 100 miles of Bogota, but each group covers quite a superficial area, and no one of them lies at a lower level than 2,000 feet above the sea or at a greater than 7,000 feet. From May, 1904, to February, 1905, the production from Muzo (the only mine then worked) was 262,548 carats of first quality, 467,690 carats of second quality, 22,700 carats of third quality, and 16,000 carats of fourth quality, with a total value of $900,000.

The Muzo group is called the "Mina Real" (Royal mine), and has been worked from time immemorial, but a Spanish soldier, Juan Penazon (or Penajos) definitely located them in 1558. The first scientific examination

Iwas made in 1704. A report from the English company states that the cost of mining is about $97,000 a year, not including the payment for the monopoly. The number of workmen has been upward of 300, varying according to the company's activity. Some stealing goes on, one estimate placing it as high as 25 per cent of the output. Although, including pre-Colombian mining and what has been extracted within the last four centuries, great quantities of emeralds have been sent all over the world, from the great extent of the areas containing deposits and the innumerable ramifications of the strata in which emeralds are found, it would seem quite within reason to hope that the supply of the beautiful precious stone will not be exhausted for many generations yet to come.-[Bulletin Pan-American Union.]

ABOUT SUGAR

HE average consumption of sugar per capita has nearly doubled in the United States since 1881. It is now 80 pounds a year, making a total of 8 billion pounds..

Fifty-five per cent of the sugar used in the United States comes from foreign countries, 23 per cent from domestic sources and 22 per cent from our insular possessions-Hawaii, Porto Rico, and the Philippines.

Two-thirds of the beet sugar produced in the United States comes from California, Colorado and Michigan.

Substantially all of our domestic cane sugar is produced in south-eastern

Louisiana.

An acre of Louisiana cane produces 2,500 to 3,000 pounds of sugar. An acre of beets produces about the same amount; an acre of cane in Hawaii produces from 8,000 to 10,000 pounds of sugar.

We import practically no refined sugar; it is received in the raw state. The United States is the world's greatest importer of this commodity.

A little more than half of the world's output of sugar is from cane. About 80 per cent of the sugar which we import from foreign countries comes from Cuba.

Two-thirds of the imported sugar enters the port of New York and is refined in or near New York City.

In the order of production, the leading five cane sugar producing countries are British India, Cuba, Java, Hawaii, and Porto Rico-four of them islands. The leading five beet sugar producers are Russia, Germany, Austria-Hungary, United States, and France.

While British India ranks first as a sugar producer, it ranks 22nd as an exporter, and third as an importer; in other words, in addition to its own production of 22 million tons, India uses 600,000 tons of imported sugar. China, on the other hand, uses only about 11⁄2 pounds per capita annually.

R. H. W.