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...leum]], [[natural gas]], [[gold]], [[silver]], [[chrome]], [[asbestos]], [[manganese]], [[gypsum]], [[mica]], [[zinc]], [[iron]], [[lead]], [[uranium]], [[coppe

...he 19th century, the color of amethyst was attributed to the presence of [[manganese]]. However, since it is capable of being greatly altered and even discharge

...usually considered as due to trace amounts of [[titanium]], [[iron]], or [[manganese]], in the massive material. Some types of quartz contain microscopic [[ruti