LAPIS LAZULI  , or

azure stone,' a mineral substance valued for decorative purposes in consequence of the fine blue colour which it usually presents . It appears to have been the sapphire of ancient writers: thus Theophrastus describes the u6irOetpos as being spotted with gold-dust, a description quite inappropriate to modern sapphire, but fully applicable to lapis lazuli, for this stone frequently contains disseminated particles of iron-pyrites of gold-like appearance . Pliny, too, refers to the sapphirus as a stone sprinkled with specks of gold; and possibly an allusion to, the same character may be found in Job xxviii . 6 . The Hebrew sappir, denoting a stone in the High Priest's breastplate, was probably lapis lazuli, as acknowledged in the Revised Version of the Bible . With the ancient Egyptians lapis lazuli was a favourite stone for amulets and ornaments such as scarabs; it was also used to a limited extent by the Assyrians and Babylonians for cylinder seals . It has been suggested that the Egyptians obtained it from Persia in exchange for their emeralds . When the lapis lazuli contains pyrites, the brilliant spots in the deep blue matrix invite comparison with the stars in the firmament . The stone seems to have been sometimes called by ancient writers Kuavos . It was a favourite material with the Italians. of the Cinquecento for vases, small busts and other ornaments . Magnificent examples of the decorative use of lapis lazuli are to be seen in St Petersburg, notably in the columns of St Isaac's cathedral . The beautiful blue colour of lapis lazuli led to its employment, when ground and levigated, as a valuable pigment known as ultramarine (q.v.), a substance now practically displaced by a chemical product (artificial ultramarine) .

Lapis lazuli occurs usually in compact masses, with a finely granular structure; and occasionally, but only as a

great rarity, 1 The Med . Gr . Xaj'oipcov, Med . Lat. lazurius or lazulus, as the names of this mineral substance, were adaptations of the Arab. al-lazward, Pers. lajward, blue colour, lapis lazuli . The same word appears in Med . Lat. as azura, whence O.F. azur, Eng . " azure," blue, particularly used of that colour in heraldry (q.v.) and represented conventionally in black and white by horizontal lines . it presents the form of the rhombic dodecahedron . Its specific gravity is 2.38 to 2.45, and its hardness about 5'5, so that being comparatively soft it tends, when polished, to lose its lustre rather readily . The colour is generally a fine azure or rich Berlin blue, but some varieties exhibit green, violet and even red tints, or may be altogether colourless . The colour is sometimes improved by heating the stone . Under artificial illumination the dark-blue stones may appear almost black .

The mineral is opaque, with only slight translucency at thin edges . Analyses of lapis lazuli show considerable variation in

composition, and this led long ago to doubt as to its homogeneity . This doubt was confirmed by the microscopic studies of L . H . Fischer, F . Zirkel and H . P . J . Vogelsang, who found that sections showed bluish particles in a white matrix; but it was reserved for Professor W . C . Brogger and H . Backstrom, of Christiania, to separate the several constituents and subject them to analysis, thus demonstrating the true constitution of lapis lazuli, and proving that it is a rock rather than a definite mineral species .

The essential

part of most lapis lazuli is a blue mineral allied to sodalite and crystallized in the cubic system, which Bragger distinguishes as lazurite, but this is intimately associated with a closely related mineral which has long been known as hauyne, or hauynite . The lazurite, sometimes regarded as true lapis lazuli, is a sulphur-bearing sodium and aluminium silicate, having the formula: Na4(NaS3AI) Al2 (SiO4)3 . As the lazurite and the hauynite seem to occur in molecular intermixture, various kinds of lapis lazuli are formed; and it has been proposed to distinguish some of them as lazurite-lapis and ha-dyne-lapis, according as one or the other mineral prevails . The lazurite of lapis lazuli is to be carefully distinguished from lazulite, an aluminium-magnesium phosphate, related to turquoise . In addition to the blue cubic minerals in lapis lazuli, the following minerals have also been found: a non-ferriferous diopside, an amphibole called, from the Russian mineralogist, koksharovite, orthoclase, plagioclase, a muscovite-like mica, apatite, titanite, zircon, calcite and pyrite . The calcite seems to form in some cases a great part of the lapis; and the pyrite, which may occur in patches, is often altered to limonite . Lapis lazuli usually occurs in crystalline limestone, and seems to be a product of contact metamorphism . It is recorded from Persia, Tartary, Tibet and China, but many of the localities are vague and some doubtful . The best known and probably the most important locality is in Badakshan . There it occurs in limestone, in the valley of the river Kokcha, a tributary to the Oxus, south of Firgamu . The mines were visited by Marco Polo in 1271, by J . B .

Fraser in 1825, and by Captain John Wood in 1837—1838 . The rock is split by aid of fire . Three varieties of the lapis lazuli are recognized by the miners: nili of indigo-blue colour, asmani sky-blue, and sabzi of green tint . Another locality for lapis lazuli is in Siberia near the western extremity of Lake Baikal, where it occurs in limestone at its contact with granite . Fine masses of lapis lazuli occur in the Andes, in the vicinity of Ovalle, Chile . In Europe lapis lazuli is found as a rarity in the peperino of Latium, near Rome, and in the ejected blocks of Monte Somma, Vesuvius . (F . W .