Ruth Moyer, age 7, of Allentown, Pennsylvania, for her question:

Which is the most valuable Gem?

If you had to guess, you would say that the diamond is the world's most precious gem. Often it is. But diamonds come in different sizes and also in different qualities. Chips of dirty looking diamonds are useful in industry because diamond is the hardest cutting stone, But such diamonds are not very costly. A jeweler rates the value of a gem on its brilliance, its color and whether or not it has cracks or flaws. A flawless, blue white diamond that sparkles with brilliance is rated tops. And, naturally, the bigger it is, the more valuable it is. Sometimes a beautifully colored diamond is considered more precious than a white or glassy clear one. For example, a brilliant and flawless diamond of deep heavenly blue may be more costly than a clear one of the same size.

Colored gems are more beautiful to some people. Some of them are very rare and this adds to their value. A perfect Oriental sapphire may be more costly than a fine diamond. It is judged on the quality of its heavenly blue and the buried fingers of light that form a star. A fine Oriental ruby, an Oriental topaz or an Oriental emerald may also be more valuable than a fine diamond. The value of these gems depends upon many things and even experts cannot put exact price tags on them.