According to tables furnished by the De Beers Company, the yield of the De Beers and Kimberley mines has declined as the depth increases. At the same time the value of the stones has risen, and diamonds are more expensive to-day than at any previous time. NUMBER OF VALUE YEAR CARATS[5] PER CARAT PER LOAD _s._ _d._ 1889 1·283 19 8·75 1890 1·15 32 6·75 1891 0·99 29 6 1892 0·92 25 6 1893 1·05 29 0·6 1894 0·89 24 5·2 1895 0·85 25 6 1896 0·91 26 9·4 1897 0·92 26 10·6 1898 0·80 26 6·2 1899 0·71 29 7·2 1900 0·67 35 10·2 1901 0·76 39 7 1902 0·76 46 5·7 1903 0·61 48 6·3 1904 0·54 48 11·8 STONES OTHER THAN DIAMONDS Accompanying diamonds in the concentrates are a number of other minerals of high specific gravity, and some of notable beauty. Among these are the rich red pyrope (garnet), sp. gr. 3·7, containing from 1·4 to 3 per cent of oxide of chromium; zircon, in flesh-coloured grains and crystals, sp. gr. 4 to 4·7; kyanite, sp. gr. 3·45 to 3·7, discernible by its blue colour and perfect cleavage; chrome diopside, sp. gr. 3·23 to 3·5, of a bright green colour; bronzite, sp. gr. 3·1 to 3·3; magnetite, sp. gr. 4·9 to 5·2; mixed chrome and titanium iron ore, sp. gr. 4·4 to 4·9, containing from 13 to 61 per cent of oxide of chromium, and from 3 to 68 per cent of titanic acid, in, changeable quantities; hornblende, sp. gr. 2·9 to 3·4; barytes, sp. gr. 4·3 to 4·7; and mica. Some of the garnets are of fine quality, and one was recently cut which resembled a pigeonblood ruby, and attracted an offer of £25. In the pulsator and sorting house most of the native labourers are long-sentence convicts, supplied with food, clothing, and medical attendance by the Company. They are necessarily well guarded. I myself saw about 1000 convicts at work. I was told that insubordination is very rare; apart from the hopelessness of a successful rising, there is little inducement to revolt; the lot of these diamond workers is preferable to life in the Government prisons, and they seem contented. [Illustration: FIG. 10. DE BEERS DIAMOND OFFICE. 25,000 CARATS.] [Illustration: FIG. 11. DE BEERS DIAMOND OFFICE. THE VALUATORS’ TABLE. To face p. 72.] CHAPTER V THE DIAMOND OFFICE