The use of amber for artistic and decorative purposes has declined considerably since the Middle Ages, but magnificent illustrations of its employment for these purposes are to be seen in many European museums, notably the Green Vaults of Dresden. Though so soft and easily destructible a substance it endures with ordinary care as well as the hardest stone, and works of art formed from amber are as well preserved as any to be found. MALICHITE. Malachite is a green opaque mineral whose color indicates a salt of copper. It is a carbonate of copper containing water, the percentages being in the typical mineral, cupric oxide 71.9, carbon dioxide 19.9, and water 8.2. It is the common form which copper assumes when it or even its ores oxidize in the air. Many of the green stains on rocks or minerals can be correctly referred to malachite. It is only valued for ornamental purposes however when it occurs in compact masses usually exhibiting concentric layers. Malachite in this form takes a fine polish. Malachite is not a hard mineral, its hardness being between 3.5 and 4. It can therefore be scratched with a knife. It is comparatively heavy, weighing four times as much as an equal bulk of water. When heated before the blowpipe it fuses easily, coloring the flame green. By heating long enough on charcoal it can be made to yield a globule of copper. It is easily attacked by common acids, causing effervescence of carbon dioxide. This test can be used to distinguish it from the silicate of copper, chryscolla, which has the same color. Besides its occurrence in massive forms as noted above Malachite not uncommonly occurs in tufts and rosettes incrusting other minerals. This is an especially common occurrence in mines in Arizona and affords specimens of great beauty especially when the green tufts of malachite are seen upon brown limonite, for then the appearance of moss on wood is closely simulated. Such material is of course too fragile to be used for decorative purposes. Malachite is prepared for ornamental use by sawing masses of the character of those previously referred to into thin strips which are then fastened as a veneer on vessels of copper, slate or other stone previously turned to the desired shape. Putting pieces together so that neither by their outlines nor color will it appear that they are patchwork requires a high degree of skill and such work is done almost exclusively in Russia. Table tops, vases and various other vessels are manufactured in this way and form objects of great beauty. The pillars of the Church of Isaac in St. Petersburg are of malachite prepared in this way and there are similar pillars in the Church of St. Sophia, Constantinople, said to have been taken from the Temple of Diana at Ephesus.