The color most common in pearls of all seas is yellow, but it is not so with fresh-water ones. Other colors are seldom found except as tints in white pearls, but distinctly yellow oriental pearls are abundant. The tones of color in the white are, yellow, blue, pink and green. They are so slight that it is difficult to recognize them except by comparison. The blue and pink are considered best, the champions of each being about equal. The green come next in favor and the yellow last. This order applies fully however to the Occident only. Some Oriental peoples do not draw such fine distinctions, and the Chinese prefer the creamy yellow to any other.
The "blue" pearls, or "Panama" pearls as they are sometimes called in the trade, must not be confounded with the blue white pearls just mentioned. "Blue" pearls are of a dingy, slaty blue tint. They have a dark appearance and the luster is seldom good. As many of this character are found in the Panama waters such pearls are often sold as "Panama" pearls. They are even less desirable than those which are decidedly yellow, though persons of a little knowledge will often buy them in preference to others which are better, because they are not yellow and are cheap.
"Fancies" include all decided colors, or those having a rare and beautiful tint. Yellow pearls as generally found are not classed among them because the color is not fine, but dark,— "brackish" one might term it. A clean buttercup yellow, or an orange yellow, would be "fancy" however. On the other hand a deep pink is seldom fine as the color is then almost invariably muddy, whereas the clean delicate light pink pearls are rare and highly esteemed. A clear grass green is never seen but the color occurs in very beautiful bronze and peacock shadings. Various shades of blue, rose, copper, and red with bronze effects, and black are included in this classification.
Black pearls are much prized, and the term covers a wide range of dark shades of gray, slate, brown and red. The ideal color however is sufficiently deep to be, as the name indicates, black, though it has not the metallic appearance of hematite, nor the polished shine of the black clam pearl. Black pearls having a bronze effect are open to suspicion, especially if they are pierced, as many of them are artificially colored and are liable to fade. Such pearls have a somewhat metallic appearance, are seldom very lustrous, and if there is a rough chalky place in the skin it will be blacker there than elsewhere.
It is difficult to give rules by which to judge color, but there is a quality which can only be described as "clean." It is free from muddiness and is desirable in pearls as in all other gems.
The proportion of fancy colors is greater in fresh-water pearls than in the orientals. In the United States the fisheries which have yielded the finest "fancies" are those of Wisconsin, Kentucky and Tennessee. Of sea pearls, most of the fine black ones come from the coasts of Mexico. Beautiful colored pearls are found in fisheries of the Oceanic Islands, for instance at the Isles of New Caledonia and Gambier, and in China and Japan.
To make close comparisons of color in pearls, place them on white cotton under or opposite a strong natural light. To judge shape and luster, roll them on black cloth. These are the most trying conditions and it should be remembered by those who test them thus, that no position as jewels when worn can be so unfavorable or trying.