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Streak & Color

Colors to Analyze                                
Upon finding a mineral, one's first instinct might be to report its color. There are some minerals for which this is very helpful -- azurite is always blue and galena is always silver, for example -- but some minerals can come in any color, (e.g., calcite, quartz, fluorite) and most do come in more than one. In addition, many colors are shared by multiple minerals, and a surface which has been exposed to the elements can change in color.
However, there is one color which is important to mineral identification: the color of a mineral's streak. Using either a streak plate or any unglazed porcelain surface (the back of an old tile works well), grind the mineral until it leaves just enough powder that you can identify the powder's color. The powder is usually the same color as the mineral, but not always. However, with very few exceptions the color of a mineral's streak will be constant regardless of the mineral's color, so it provides an excellent method to elimate many mineral candidates as you attempt to identify a specimen.
Advanced chemical analysis may involve analyzing the color of the flame produced by a mineral under specific circumstances.

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