Moldavite, which differs in no respect from ordinary green bottle-glass, is of interest on account of its problematical origin. Its occurrence in various parts of Bohemia and Moravia cannot be explained as the result of volcanic agency. It may possibly be the product of old and forgotten glass factories which at one time existed on the site. Even meteorites have been suggested as the source. The physical characters are the same as those of ordinary glass: refraction single, index 1·51; specific gravity 2·50 and hardness 5½ on Mohs’s scale. Moldavite also passes under the names of bottle-stone, or water-chrysolite. A natural glass of the same character has been found in water-worn fragments in Ceylon, and has been sold as peridot, which it resembles in colour, but is readily distinguished from it by its very different physical properties. PART II—SECTION C ORNAMENTAL STONES CHAPTER XXXIX FLUOR, LAPIS LAZULI, SODALITE, VIOLANE, RHODONITE, AZURITE, MALACHITE, THULITE, MARBLE, APOPHYLLITE, CHRYSOCOLLA, STEATITE OR SOAPSTONE, MEERSCHAUM, SERPENTINE Space will not permit of more than a few words concerning the more prominent of the numerous mineral species which are employed for ornamental purposes in articles of virtu or in architecture, but which for various reasons cannot take rank as gem-stones. Fluor, a beautiful mineral which is found in its greatest perfection in England, has enjoyed well-deserved popularity when worked into vases or other articles. The finest material, deep purple in colour, known as ‘Blue John,’ came from Derbyshire, but the supply is now exhausted. The crystallized examples, from Durham, Devonshire, and Cornwall, form some of the most attractive of museum specimens. The crystals take the shape of cubes, often twinned, and have an easy octahedral cleavage. The refraction is single, the index being 1·433. Fluor is noted for its property of appearing of differing colour by reflected and transmitted light, and the phenomenon is in consequence known as fluorescence. The specific gravity is 3·18, and the hardness 4 on Mohs’s scale. Owing to its low refraction and softness, fluor is not suitable for jewellery. Clear colourless material is in demand for particular lenses of microscope objectives.