Prase

Originally, the varietal name "prase" was applied to a dull leek-green colored quartzite (a rock, not a mineral*); but over the years it has been also applied to other materials, particularly a green colored jasper of similar color. For perhaps more than a century it was restricted to granular micro-crystalline varieties of quartz and the original quartzite; but in recent years euhedral crystals of quartz having a similar leek-green color have had the term applied to them as well, expanding the definition beyond micro-crystalline forms. Now it is simply a color descriptor for quartz: If it is leek-green, it is called "prase" - whether it is micro- or macro-crystalline, and no matter what causes the color. Basically, the term no longer has any scientific rigor - it has become a general term; it can't even truly be called a varietal name any longer - since it covers more than one material. * However, the original German definition of "Prasem" is that of a quartz, in crystals or massive, which is coloured leek-green by acicular inclusions of "Strahlstein" (= actinolite ) (Gürich, 1900; Klockmann, 1912). Compare also plasma and prasiolite.