Page:The fairy tales of science.djvu/312

 mineral treasures. Quartz is formed of pure silica, and is often found crystallized in beautiful six-sided prisms, ending in six-sided pyramids. When coloured by slight admixtures of other substances, such as iron and manganese, quartz goes under various names, according to the variety and arrangement of colours, crystalline form, and state of transparency. When purple, it is called amethyst, and is highly prized by you mortals; smoky quartz is called cairngorm; when blue, it is known as siderite; and when yellow, as Scotch or Bohemian topaz. Agate, jasper, carnelian, onyx, chalcedony and opal, are merely varieties of the same abundant substance. The emerald, again, one of the most esteemed gems, is nothing but transparent flint, coloured green by oxide of chromium.

"My time is precious, and although I have given you but an imperfect idea of the mineral treasures that I have to guard, I must now leave you, as my presence is required at the diamond mines of Brazil. The inferior gnomes under my control are continually engaged in building up new minerals, in filling empty veins with spar, in polishing crystals, and in performing a thousand mysterious processes of a chemical or electrical nature. It is no easy task, I can assure you, to superintend these countless operations, and I need scarcely tell you that my time is fully occupied—so, farewell!" The gnome takes off his jewelled cap, makes a low bow, and disappears.