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Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystals. [6]
The net result of cutting is two products, the waste or excess material, and the finished part. In woodworking, the waste would be sawdust and excess wood. In cutting metals the waste is chips or swarf and excess metal. Cutting processes fall into one of three major categories: Chip producing processes most commonly known as machining
Amethyst loses its natural violet color when heated to above 200-300°C and turns a color that resembles natural citrine, but is often more brownish. [45] Unlike natural citrine, the color of heat-treated amethyst comes from trace amounts of the iron oxide minerals hematite and goethite .
Herkimer diamonds became widely recognized after workmen discovered them in large quantities while cutting into the Mohawk River Valley dolomite in the late 18th century. Geologists discovered exposed dolomite in Herkimer County outcroppings and began mining there, leading to the "Herkimer diamond" moniker.
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Quartzite is a very hard rock composed predominantly of an interlocking mosaic of quartz crystals. The grainy, sandpaper-like surface is glassy in appearance. Minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization, causing streaks and lenses to form within the quartzite. [1]
Under cross polarized light (XPL) quartz displays low interference colors and is usually the defining mineral used to determine if the thin section is at standardized thickness of 30 microns as quartz will only display up to a very pale yellow interference color and no further at that thickness, and it is very common in most rocks so it will ...
Citrine / ˈ s ɪ t r iː n / is a colour, the most common reference for which is certain coloured varieties of quartz which are a medium deep shade of golden yellow.Citrine has been summarized at various times as yellow, greenish-yellow, brownish yellow or orange.