MINERALS IN ART AND ARCHEOLOGY — GETTENS 553 



The close relationship of calcite alabaster to onyx marble has been 

 mentioned. Onyx marble is a banded calcite from shelf deposits 

 formed about the orifices of hot springs. It is often beautifully 

 tinted by metallic impurities and, because of its translucency and 

 color, was used by the pre-Coliunbian inhabitants of Mexico for 

 carving masks for religious purposes. A fine example of a pale 

 green onyx marble mask is shown as frontispiece in the catalog of 

 the Robert Woods Bliss collection of pre-Columbian art [3] . 



In Europe including England alabaster is the name given to a mas- 

 sive and compact form of gypsum, calcium sulphate dihydrate (CaS04 • 

 2II2O), of fine texture which is usually white and translucent. It 

 is nearly as soft and as easy to work as soapstone and has been used 

 especially in Italy since Roman times for carving vases and statuary. 

 It is too soft and too easily weathered for general sculpture purposes, 

 but was used extensively in England for the carving of tomb figures 

 and for interior architectural ornamentation [4]. The gypsum was 

 quarried in the Middle Ages near Tutbury in Stailordshire and near 

 Derby. Many of the English alabaster sculptures were painted and 

 gilded ; a fine example is the painted alabaster figure of Saint George 

 and the Dragon in the National Gallery of Art, Washington (pi. 1, 

 fig. 2) . The Hildburgh collection of English alabasters at the Victo- 

 ria and Albert Museum, London, has many religious images and narra- 

 tive panels in gypsum alabaster [5]. The so-called "Mosul Marble" 

 used by the Assyrians is gypsum grading into anhydrite. Good ex- 

 amples are the winged human-headed lions from the palace of Sar- 

 gon II at Khorsabad which now stand in the entrance to the Assyrian 

 Galleries in the British Museum [6]. Gypsum has long been em- 

 ployed in Italy and in other areas for the production of ornamental 

 vases, statuettes, and small stele for indoor use. 



The anliydrous form of calcium sulphate called anhydrite (CaS04) , 

 although plentiful, had more limited use as a sculpture medium, but 

 at both the Metropolitan Museum of Art and the Brooklyn Museum 

 (pi. 2, fig. 1), one can see attractive bowls, vases, and figurines cut 

 by the ancient Egyptians from a pale bluish variety of anhydrite. 

 Both gypsum and anhydrite had another important use in art, which 

 was for making plaster for wall construction and for casting pur- 

 poses, but those uses will be discussed later. 



The sedimentary rocks, limestone, sandstone, and slate, and the 

 igneous rocks of composite minerals like granite, porphyry, and di- 

 orite have been transformed into beautiful and transportable objects 

 by the sculptor's hammer, but these more common and massive forms 

 of mineral and rock are not within the scope of this essay. We think 

 of them mainly as architectural media. 



There is a group of minerals, however, sometimes called semipre- 

 cious stones, which have been used since prehistoric times for minia- 



