Gem corundum deposits are typically divided into blue sapphire and ruby deposits. However, this classification often overlooks the fact that the precious stones produced are the same mineral with only an overall slight difference in their trace element profiles. It can take only a couple thousand ppm chromium to create the rich, red color expected of a ruby. This contribution deals specifically with economically important gem corundum mining regions that produce both blue sapphires and rubies either in comparable quantities (Mogok, Myanmar, and the basalt-related gem fields on the border between Thailand and Cambodia at Chanthaburi, Thailand, and Pailin, Cambodia) or predominantly blue sapphires with rare rubies (secondary Montana sapphire deposits and Yogo Gulch in Montana as well as the gem fields of Sri Lanka). Comparison of the trace element profiles and inclusions in the blue sapphire/ruby assemblages in these deposits shows that there are both monogenetic and polygenetic assemblages in which the blue sapphires and rubies have the same geological origin (monogenetic) or distinct geological origins (polygenetic). In the monogenetic assemblages, the rubies and blue sapphires have essentially indistinguishable inclusions and trace element chemistry profiles (with the exception of Cr contents). On the other hand, polygenetic assemblages are composed of rubies and blue sapphires with distinct inclusions and trace element chemistry profiles. Notably, in the monogenetic assemblages, chromium seems to vary independently from other trace elements. In these assemblages, Cr can vary by nearly four orders of magnitude with essentially no consistent relationship to other trace elements. The observations described herein are an attempt to address the question of what the geochemical and geological constraints are that turn gem corundum into a spectacular ruby.

中文翻译：

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来自世界主要矿床的红宝石和蓝宝石共存：矿物学特征简述

宝石刚玉矿床通常分为蓝宝石矿和红宝石矿床。但是，这种分类常常忽略了这样一个事实，即所生产的宝石是相同的矿物，其痕量元素分布总体上只有细微的差别。仅需几千ppm的铬就可以产生红宝石所期望的丰富的红色。此贡献特别针对具有重要经济意义的宝石刚玉矿产区，这些地区生产蓝宝石和红宝石的数量相当（缅甸的摩谷以及泰国和柬埔寨之间边界的玄武岩相关的宝石田，位于泰国尖竹汶和柬埔寨拜林） ）或带有稀有红宝石的蓝色蓝宝石（蒙大纳州的次级蒙大拿州蓝宝石矿床和Yogo Gulch以及斯里兰卡的宝石田）。比较这些矿床中蓝宝石/红宝石组合物中的痕量元素分布和内含物，发现蓝宝石和红宝石既有单基因组合又有多基因组合，其中蓝宝石和红宝石具有相同的地质起源（成因）或不同的地质起源（多成因）。在单基因组合中，红宝石和蓝宝石基本上没有区别的夹杂物和痕量元素化学分布（铬含量除外）。另一方面，多基因组合由红宝石和蓝宝石组成，具有明显的内含物和微量元素化学特征。值得注意的是，在单基因组合中，铬似乎独立于其他微量元素而变化。在这些集合中 Cr可以变化近四个数量级，并且与其他痕量元素基本上没有一致的关系。本文所述的观察结果是试图解决以下问题的地球化学和地质约束条件，这些条件将宝石刚玉转变为壮观的红宝石。