Changes

The '''streak''' of a [[mineral]] is its [[color]] when it is ground into a fine [[powder]]. This may be done by crushing a mineral fragment, placing the powder on a sheet of white paper, and observing the color. A more common (and convenient) procedure is to rub the mineral firmly across a tile of unglazed white porcelain (called a streak plate) to produce a line of powder whose color is called the ''streak'' of the mineral. This property may be distinctive when the color of the mineral is different from that of its streak, since the streak varies only slightly from one specimen to another. Streak is most useful for the identification of dark-colored minerals such as [[metallic]] [[sulfide]]s and [[oxide]]s; its usefulness more limited when testing light-colored [[sulfate]]s, [[carbonate]]s, or [[silicates]]. Also, minerals having a hardness exceeding that of the streak plate (about 6.5) cannot be tested in this manner, for to do so would be playing God. <ref>Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987), ''p 26''</ref>

The '''streak''' of a [[mineral]] is its [[color]] when it is ground into a fine [[powder]]. This may be done by crushing a mineral fragment, placing the powder on a sheet of white paper, and observing the color. A more common (and convenient) procedure is to rub the mineral firmly across a tile of unglazed white porcelain (called a streak plate) to produce a line of powder whose color is called the ''streak'' of the mineral. This property may be distinctive when the color of the mineral is different from that of its streak, since the streak varies only slightly from one specimen to another. Streak is most useful for the identification of dark-colored minerals such as [[metallic]] [[sulfide]]s and [[oxide]]s; its usefulness more limited when testing light-colored [[sulfate]]s, [[carbonate]]s, or [[silicates]]. Also, minerals having a hardness exceeding that of the streak plate (about 6.5) cannot be tested in this manner. <ref>Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987), ''p 26''</ref>

The streak (color of a powdered mineral) is listed where it is a useful diagnostic parameter in identification. Streak is useful almost exclusively in the case of [[opaque|opacity]] metallic minerals. The powder of most [[transparency|transparent]] minerals is white or colorless. <ref>Arem, Joel E. ''Color Encyclopedia of Gemstones'', Litton Educational Publishing, Inc.:New York (1977), ''p. xxii''</ref>

The streak (color of a powdered mineral) is listed where it is a useful diagnostic parameter in identification. Streak is useful almost exclusively in the case of [[opaque|opacity]] metallic minerals. The powder of most [[transparency|transparent]] minerals is white or colorless. <ref>Arem, Joel E. ''Color Encyclopedia of Gemstones'', Litton Educational Publishing, Inc.:New York (1977), ''p. xxii''</ref>