在平凡的學習、工作、生活中，大家都經常看到作文的身影吧，作文是人們把記憶中所儲存的`有關知識、經驗和思想用書面形式表達出來的記敘方式。那麼問題來了，到底應如何寫一篇優秀的作文呢？下面是小編整理的黃玉英語作文，僅供參考，大家一起來看看吧。
topaz is a hard, transparent mineral. it is a compound of aluminum, silica, and fluorine. gem topaz is valuable. jewelers call this variety of the stone "precious topaz". the best-known precious topaz gems range in color from rich yellow to light brown or pinkish red. topaz is one of the hardest gem minerals. in the mineral table of hardness, it has a rating of 8, which means that a knife cannot cut it, and that topaz will scratch golden variety of precious topaz is quite uncommon. most of the world＇s topaz is white or blue. the white and blue crystals of topaz are large, often weighing thousands of carats. for this reason, the value of topaz does not depend so much on its size as it does with diamonds and many other precious stones, where the value increases about four times with each doubling of weight. the value of a topaz is largely determined by its quality. but color is also important: blue topaz, for instance, is often irradiated to deepen and improve its color.
blue topaz is often sold as aquamarine and a variety of brown quartz is widely sold as topaz. the quartz is much less brilliant and more plentiful than true topaz. most of it is variety of amethyst: that heat has turned brown.
