Probably the largest and finest aquamarine crystal ever seen was one found by a miner on March 28, 1910, at a depth of 15 ft. (5 m.) in a pegmatite vein at Marambaya, near Arassuahy, on the Jequitinhonha River, Minas Geraes, Brazil. It was greenish blue in colour, and a slightly irregular hexagonal prism, with a flat face at each end, in form; it measured 19 in. (48·5 cm.) in length and 16 in. (41 cm.) in diameter, and weighed 243 lb. (110·5 kg.); and its transparency was so perfect that it could be seen through from end to end (Plate XXVI). The crystal was transported to Bahia, and sold for $25,000 (£5133). [Illustration: _PLATE XXVI_ LARGE AQUAMARINE CRYSTAL (_one-sixth natural size_), FOUND AT MARAMBAYA, MINAS GERAES, BRAZIL] PART II—SECTION B SEMI-PRECIOUS STONES CHAPTER XXI TOPAZ Topaz is the most popular yellow stone in jewellery, and often forms the principal stone in brooches or pendants, especially in old-fashioned articles. It is a general idea that all yellow stones are topazes, and all topazes are yellow; but neither statement is correct. A very large number of yellow stones that masquerade as topaz are really the yellow quartz known as citrine. The latter is, indeed, almost universally called by jewellers topaz, the qualification ‘Brazilian’ being used by them to distinguish the true topaz. Many species besides those mentioned yield yellow stones. Thus corundum includes the beautiful ‘oriental topaz’ or yellow sapphire, and yellow tourmalines are occasionally met with; the yellow chrysoberyl always has a greenish tinge. Topaz is generally brilliant-cut in front and step-cut at the back, and the table facet is sometimes rounded, but the colourless stones are often cut as small brilliants; it takes an excellent and dazzling polish.