Among the “blue and white” wares of all periods, the Hsüan Tê porcelain is unanimously voted the first place by Chinese writers, and its excellence is ascribed principally to the superior quality of an imported mineral variously described as _su-ni-p’o_, _su-p’o-ni_ and _su-ma-ni_. These outlandish names are, no doubt, attempts to render in Chinese the foreign name of the material, which was itself probably the name of the place or people whence it was exported. There is little doubt that this mysterious substance was the same species as the Mohammedan blue (_hui hui ch’ing_) of the following century. Indeed, this latter name is applied to it in Hsiang’s Album. The Mohammedan blue was obtained from Arab traders, and its use for painting on pottery had been familiar in the Near East, in Persia and Syria for instance, at least as early as the twelfth century.[35] The _su-ni-p’o_ blue was no doubt imported in the form of mineral cobalt, and though there was no lack of this mineral in the neighbourhood of Ching-tê Chên, the foreign material was of superior quality. It was, however, not only expensive but unsuited for use in a pure state. If applied by itself, it had a tendency to run in the firing, and it was necessary to blend it with proportions of the native mineral varying from one in ten for the finest quality to four in six for the medium quality. The native mineral used by itself tended to be heavy and dull in tone, owing to its inability to stand the intense heat of the kiln, and was only employed alone on the coarser wares. The supply of Mohammedan blue was uncertain and spasmodic. It ceased to arrive at the end of the Hsüan Tê period, and it was not renewed till the next century (see p. 29). Its nature, too, seems to have varied, for we are expressly told that the Hsüan Tê blue was pale in tone while the Mohammedan blue of the sixteenth century was dark. Possibly, however, this was not so much due to the nature of the material as to the method of its application, for Chinese writers are by no means unanimous about the paleness of the Hsüan Tê blue. The _Ch’ing pi ts’ang_, for instance, states that “they used _su-p’o-ni_ blue and painted designs of dragons, phœnixes, flowers, birds, insects, fish and similar forms, deep and thickly heaped and piled and very lovely.” Authentic specimens of Hsüan Tê blue and white are virtually unknown, but the mark of the period is one of the commonest on Chinese porcelain of relatively modern date. In most cases this spurious dating means nothing more than that the period named was one of high repute; but there is a type of blue and white, usually bearing the period mark of Hsüan Tê, which is so mannered and characteristic that one feels the certainty that this really represents one kind at least of the Hsüan porcelain. It is usually decorated in close floral scrolls, and the blue is light dappled with darker shades, which are often literally “heaped and piled” (_tui t’o_) over the paler substratum.