 |
| Drawings of Fairy Crystal and Quartz Crystals. |
Most boys and girls know the game called ''kingdoms'' in which one has to tell whether an object belongs in the mineral, animal, or plant kingdom. Included in the mineral kingdom are rocks like granite, metals such as copper, and beautiful gem stones such as rubies and emeralds. Many precious stones occur in crystals, which have been called the flowers of the mineral kingdom.
To most people a crystal is either a clear, transparent ball or a sparkling piece of bright stone. Practically every mineral, formed under favorable conditions, will be found as crystals, which are solid substances, regularly shaped, with angles and flat surfaces. The mineral particles making up the crystal are arranged in a definite order. Scientists have separated the varying types of crystals into six classes or groups. Regardless of size or shape the same mineral will always crystallize in the same class.
The mineral with which you are most familiar is water. Usually it is a liquid, although water is also found in a solid form. Ice, hail, and snow are solid forms of water. Snowflakes are nearly perfect water crystals and each one is built about a pattern of six equally spaced points. Ice crystals are crowded so closely together that they do not have a chance to grow into perfect shapes. If you use a magnifying glass to examine a number of snowflakes you will be amazed at the variety of designs, yet each snowflake will have the same fundamental six-pointed pattern.
Another common mineral whose crystals can be easily seen is salt. Under a magnifying glass it will be observed that each tiny crystal is shaped like a cube.
Crystals are formed in a number of ways. One of the most common is by precipitation, or separation, particle by particle, from a liquid in which the mineral is dissolved. Water seeping through the ground dissolves the rocks and carries them away. As the water descends it picks up more and more mineral matter until it becomes so saturated that it can carry no more. A change in temperature or the amount of pressure on the mineral-bearing water may cause it to deposit part of its load. In the rocks there are free spaces or cavities in which crystals may form if there is a sufficiently long time for them to grow undisturbed.
Some crystals are large and others are so small that you can not see them without a microscope. In mines in South Dakota, crystals have been found forty-seven feet long and weighing thirty-seven tons. Beryl crystals weighing several tons have been found in New Hampshire.
If you care to try an experiment, it is easy to watch the formation of crystals. In a small bottle dissolve two or three tablespoonfuls of sugar in warm water. Shake the bottle until the sugar is in solution. It has then entirely disappeared. Then hang a string in the water and put the bottle away. As the water cools and evaporates the sugar will crystallize out on the string and you will have the string coated with sugar crystals. Perhaps you have found sugar crystals in syrup or honey.
Crystals sometimes play tricks and appear in fancy costumes that might be confusing except for that unchanging rule that crystals must form in the class to which they belong. Twin crystals are fairly common. One type of twin has crystals that are just alike except that one is left-handed and the other is right-handed. Their inside hands are joined together and these twins are never found separate. Other crystals have inclusions; that is, one mineral has formed around another, and in the crystal thus formed the two minerals will be seen, one inside the other.
In the Blue Ridge Mountains of Virginia interesting twin crystals are formed by the mineral staurolite. These twins are called ''fairy stones'' and are in the shape of small crosses. Staurolite crystals are dark reddish-brown in color and are not transparent. People carry them for good luck charms and there is a fairy story telling how they were formed. According to the story, fairies were dancing in the forest when a messenger brought them the sad news of the death of Jesus. So unhappy were the fairies that they wept. The tears fell to the ground where they turned to stones in the shape of crosses. Long ago the fairies vanished from the beautiful Virginia forests but the crystal crosses are still found. Pabst
More About Fairy Stone Park:
Extend The Lesson With A Simple Craft:
More About Fairy Stone Park:
Extend The Lesson With A Simple Craft:
No comments:
Post a Comment
Thanks for your thoughts. All comments are moderated. Spam is not published. Have a good day!