Tony Jackson, age 12, of Columbia, Tenn., for his question:
WHY DO WE HAVE BIRTHSTONES?
A birthstone is any of various gems associated with the particular calendar months of the year and considered lucky to people born in those months. Many experts attribute the origin of the birthstone tradition to the 12 jeweled breastplate worn by Aaron, the brother of Moses
A report of the Jewel covered breastplate is told in the Bible's second book, Exodus, chapter 39. Through the years, many myths and superstitutions gradually grew up regarding the stones and symbolic meanings or virtues were ascribed to them.
Today, five months of the year have alternate stones associated with them, while seven of the months have just a single gem called the birthstone.
October is one of the months that has two birthstones: opal and tourmaline. The gem for November is the topaz while December comes up with two: turquoise and zircon.
Birthstone for January is the garnet while the amethyst is for February. March comes up with two birthstones: aquamarine and bloodstone.
The diamond is April's birthstone while May receives the emerald. Then comes June with two: pearl and moonstone.
July's birthstone is the ruby, August has both the peridot and the sardonyx while September features the sapphire.
In general, all minerals and stones that are used for jewelry and other ornamental purposes are called gems. The word gem comes form the latin "gemma" meaning "bud."
The story of birthstones and precious gems is much like that of the blooming of flowers. Like tiny buds that burst into beautiful blossoms, dull lumps of mineral matter can.be cut and polished into brilliantly flashing or glowing gems.
One beautiful gem, the pearl, is not a stone, but is a luminescent deposit obtained from a mollusk.
Hardness is an important gem quality. Few stones can serve as gems unless they wear well.
Shape of crystals differs with each gem mineral, but all crystals in any one mineral always have the same type of symmetry. Diamonds crystalize in the isometric system either with six square faces forming a cube or with eight triangular sides which form a double pyramid.
Color is one of the important factors that determine the beauty and splendor of gems.
Opaque or cloudy gem stones depend on color alone for their beauty whereas transparent stones without a rich color may have unusual beauty because of their ability to reflect light.
There are two types of colors in gem materials: essential and nonessential. Essential color is the color of the mineral itself, when pure. Nonessential color is the result of an impurity in the mineral. Such an impurity is not an important part of the mineral. Since different specimens of a mineral may contain different impurities, each of these specimens may be a different color.
Also important in gems is the index of refraction, a measurement of the speed of rays of light passing through a mineral.