HPHT钻石.doc

Investigation of Seven Diamonds, HPHT Treated by NovaDiamond by F. De Weerdt and J. Van Royen The Journal of Gemmology, October 2000, Vol 27, No.4 The aim of HPHT treatments is to change defects in the crystal lattice under the influence of elevated temperature and pressure. At these temperature, defects can become mobile and can aggregate, thereby changing the colour of the diamond; other defects may dissociate, again leading to colour changes. The parameters used in these treatments can be similar to the pressure and temperature (1200-1300( C) of the environment where diamonds grow in nature. However in order to reduce the long aggregation time, higher temperatures (1400-2000(C or higher) and pressures (up to 70 000 atm) are used during HPHT treatments. The detection of these treatments is a major problem for diamond grading laboratories all over the world. Press releasses of the American company NovaDiamond state that the original brownish colour of type Ia diamonds is changed to yellowish-green by HPHT treament, without using irradiation. Identification of HPHT-Treated Yellow to Green Diamonds by Ilene M. Reinitz, Peter R. Buerki, etc. Gem Gemology, Summer 2000, P128-137 目前有几家公司利用高温高压（HPHT）将棕色（brown）钻石处理为绿黄色、黄绿色、黄色和褐黄 色。这些公司包括通用电器公司、Novatek以及一些俄罗斯和瑞典的公司。 GE和Novatek公开讨论他们如何处理这些钻石的细节。用合成单晶钻石相同的设备，把天然钻石置于 高压（约6 Gigapascals, 1Gpa=60 kilobars）下，短时间（少于30分钟或更短）放置于高达2100(C的高温进行处理。这些处理条件与GE在处理(decolorize diamonds) GE POL钻石时相似，但不同的是这里所处理的是含氮的Ia型棕色钻石，而GE处理的对象是IIa型钻石。高温高压处理后的钻石必须重新进行抛光以除去表面的损伤。虽然这两家所处理钻石的外观和宝石学特征很相似，但并不意味他们采用相同的高温高压的设备和处理条件。 这些高温高压处理的钻石具有以下以下特征： 颜色：色饱和度高，色调常较深。大多数颜色为绿黄色至黄绿色，在不同的灯光下绿黄色与黄绿色变化明显，尤其在阳光直射下因激发绿色光而明显地增加绿色调的组分。若这些钻石接触到通常修理珠宝的温度（高达1000(C），钻石总的色饱和度会暂时变得更浓，但一旦冷却后颜色恢复原样。 放大下观察：大多数的这类处理钻石具棕－到－黄色的面状的纹理（to be intrinsic to。纹理：weak-very strong），沿一个或多个八面体方向分布，形成带状或相交的色带。虽然天然的黄色、棕色和绿黄色钻石也有棕色的纹理（生长纹），但很少伴有黄色纹理。有些加工好的钻石显示热处理的特征，如具蚀像和蚀坑的原晶面，以及具蚀像和石墨化的裂隙，环绕晶体包裹体的应力裂隙。有一些具蚀像的表面经重抛光后仍会残留在刻面棱和原晶面上，靠表层的裂隙有时也受侵蚀或石墨化（要区别蚀像是由热处理引起的还