Sapphire blue
This blue, which is quite different from the sapphire blue, should be clear and deep, not a pale greenish blue. It is the evidence of green which makes the stone less valuable. Of course, there should be no internal lines or cracks, and the stone should be cut in diamond engagement rings good proportions, without too much depth. Depth will increase the body color, but the stone will weigh more and it will be more difficult to use in jewelry. Good aquamarines of a deep blue color, free from flaws, and well cut, may reach from $28 (£10) to $70 (£25) a carat. But the usual qualities realize about $14 (£5) a carat, and pale stones can be bought for a few shillings, or about $2 a carat. A fine aquamarine is a beautiful stone, and although difficult to obtain, it is often seen in large sizes.
With most of the colored stones, the depth of body color is the chief factor which makes for commercial value. That is to say, a deep blue turquoise is more valuable than the greenish blue stone, the deep blue lapis lazuli is better than the paler or streaked specimens, and the rich, deep purple amethyst is the shade which obtains the highest price. Internal and external flaws of 3 stone engagement rings, of course, must be absent, and size is important. With these points in mind, we can deal with the remaining well known jewel stones very quickly.
Tourmalines. Green stones should not be too dark nor too pale, and this applies to the red stones. Flawed material is not often cut or used in jewelry.