Topaz
[size=3][color=#29384e][font=Times New Roman]Topaz is a hard[/font][font=宋体]，[/font][font=Times New Roman] transparent mineral. It is a compound of aluminum[/font][font=宋体]，[/font][font=Times New Roman] silica[/font][font=宋体]，[/font][font=Times New Roman] and fluorine. Gem topaz is valuable. Jewelers call this variety of the stone[/font][font=宋体]“[/font][font=Times New Roman]precious topaz[/font][font=宋体]”。[/font][font=Times New Roman] 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[/font][font=宋体]，[/font][font=Times New Roman] it has a rating of 8[/font][font=宋体]，[/font][font=Times New Roman] which means that a knife cannot cut it[/font][font=宋体]，[/font][font=Times New Roman] and that topaz will scratch quartz.[/font][/color][/size][size=3][color=#29384e][font=Times New Roman] [/font][/color][/size]
[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]The golden variety of precious topaz is quite uncommon. Most of the world[/font][font=宋体]‘[/font][font=Times New Roman]s topaz is white or blue. The white and blue crystals of topaz are large[/font][font=宋体]，[/font][font=Times New Roman] often weighing thousands of carats. For this reason[/font][font=宋体]，[/font][font=Times New Roman] the value of topaz does not depend so much on its size as it does with diamonds and many other precious stones[/font][font=宋体]，[/font][font=Times New Roman] 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[/font][font=宋体]：[/font][font=Times New Roman] blue topaz[/font][font=宋体]，[/font][font=Times New Roman] for instance[/font][font=宋体]，[/font][font=Times New Roman] is often irradiated to deepen and improve its color.[/font][/color][/size]
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[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]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[/font][font=宋体]：[/font][font=Times New Roman] that heat has turned brown.[/font][/color][/size]
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[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]NOTE[/font][font=宋体]：[/font][/color][/size]
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[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]topaz / [/font][font=宋体]‘’[/font][font=Times New Roman]t[/font][font=宋体]э[/font][font=Times New Roman]up[/font][font=宋体]ж[/font][font=Times New Roman]z[/font][font=宋体]；[/font][font=Times New Roman] `top[/font][font=宋体]ж[/font][font=Times New Roman]z/ n [/font][font=宋体]（[/font][font=Times New Roman]a[/font][font=宋体]）[/font][font=Times New Roman] [U] transparent yellow mineral[/font][font=宋体]黄玉（矿物）。[/font][/color][/size]
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[color=#29384e][font=宋体][size=10.5pt] （[/size][/font][size=10.5pt]b[/size][font=宋体][size=10.5pt]）[/size][/font][size=10.5pt] [C] semi-precious gem cut from this[/size][font=宋体][size=10.5pt]黄玉；黄宝石[/size][/font][/color]
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