Brendalea Hubbard, age 10, of Victoria, B.C Canada, for her question:

How does topaz differ from corundum?

Topaz is a glassy crystal, tinted with lemon or sunbeam colors. The earth has several recipes for making topaz from different ingredients. The value of the topaz depends upon the mineral ingredients nature uses to make it. The most precious topaz is made from a mineral called corundum.

Nature's gem stones are made from the same minerals used to make the ordinary rocks in the ground. Carbon atoms can be arranged to make soft, sooty graphite or hard, glassy diamonds. The gem stones are everyday atoms and molecules, arranged in compact formations to form glassy crystals. Traces of other minerals may tint the crystals with color, adding beauty and value. Ages ago, yellow tinted crystals found in the ground were named topaz. This was long before gem admirers knew that nature's jewels were made from ordinary atoms and molecules.

Now we know that nature has at least three recipes for making yellow crystals. We still call all of them topaz and though they may look alike to us, an expert can tell the difference. False topaz, or citrine, is made from silica, the plentiful. mineral used to make sand and quartz. Its molecuels can be crowded together in crystal formation and tinted with traces of color. Specks of decay may be frozen inside the glassy prison to add tints of marigold or lemonade. But this handsome yellow topaz is rated only as a semiprecious gem.

Precious topax is made from a different mineral. Its molecules contain atoms of aluminum and fluorine, silicon and oxygen. Then packed together, these molecules form a harder, brighter crystal than the quartz crystals of citrine. This mineral crystal may be glassy clear or watery blue, tinted with brown or ghostly pink. The yellow and yellow brown types are called topaz and jewelers rate them as precious gem stones.

But nature has a recipe for making a yellow crystal that is even more precious than precious topaz. Jewelers call it Oriental topaz and it is made from the mineral called corundum. The molecules of corundum are packages of ordinary aluminum and oxygen atoms. When arranged in crystal formation, they form a gem that is much harder and brighter than either precious topaz or citrine topaz. In nature, the hardest of all stones is the diamond. Corundum rates second in hardness but some of its beautiful crystals are priced above the value of diamonds. topaz

When corundum is glassy clear, it is called Oriental white sapphire. Corundum tainted with heavenly blue is Oriental sapphire. Vidlet corundum is Oriental amethyst, green corudum is Oriental emerald and the red variety is Oriental ruby. Corundum gems are far more valuable than the precious colored gems made from other minerals. And the most precious Oriental topaz is crystal corundum tinted with pale or shadowy sunbeams.

The hardest of the semiprecious gems are made of quartz and the honey colored crystals are called citrine or false topaz. Quartz tends to form six sided crystals, often in tall columns or pointed pyramids. Precious topaz is made from a harder mineral but too much heat may steal its golden glory or make it blush pink. Its sharp cornered crystals form around three lines or levels. It may form a huge pillar with smooth, sloping sides and a low sloping roof with a flat top. Oriental topaz forms crystals shaped like those of citrive, or false topaz. But experts can detect its extra hardness and other qualities of super precious corundum.