The structure of quartz was deciphered by Bragg and Gibbs in 1925 (for a review of the structure and symmetry features of quartz, see Heaney, 1994). A single specimen can be correctly classified as several varieties.įig.1: Threefold helix made of SiO 4 groups. Note that, contrary to minerals, the definitions of varieties are not mutually exclusive in the sense that no mineral can be another. More about the specific properties of chalcedony and its varieties can be found at the respective mineral pages. On Mindat, macrocrystalline quartz and its varieties are listed as quartz and varieties of quartz.Ĭryptocrystalline quartz and its varieties are listed as chalcedony, like "Quartz (Var: Chalcedony)", or as variety of chalcedony, like "Chalcedony (Var: Agate)". Mindat Classification of Quartz Varieties Because there are no canonical rules on naming or defining quartz varieties like they are for minerals, the definitions of some quartz varieties are precise and generally accepted, while the definitions of others vary considerably between different authors, or are rather fuzzy. The best known examples are the colored varieties of quartz, like amethyst or smoky quartz, but there are also trivial names for specific crystal shapes, aggregates and textures, like scepter quartz, gwindel or quartzine. Quartz crystals or aggregates that share certain peculiar physical properties have been classified as quartz varieties with specific "trivial names". Tomkeieff (1941) also noted that Erasmus Bartholinus (1669) used the various spellings for "crystal" to signify other species than quartz and that crystal could refer to other "angulata corpora" (bodies with angles): "In any case in the second half of the XVIIIth century quartz became established as a name of a particular mineral and the name crystal became a generic term synonymous with the old term 'corpus angulatum'." He referred to them as "cristallus" and "crystallus montium". In 1669, Nicolaus Steno (Niels Steensen) obliquely formulated the concept of the constancy of interfacial angles in the caption of an illustration of quartz crystals. Brown in 1685 and Johan Gottschalk Wallerius in 1747. Gradually, there were more references to quartz: E. "Quarz" was used in later literature referring to the Saxony mining district, but seldom elsewhere. Such a clumsy word as 'Querkluftertz' could easily be condensed to 'Querertz' and then to 'Quertz', and eventually become 'Quarz' in German, 'quarzum' in Latin and 'quartz' in English." Tomkeieff (1941, q.v.) noted that "quarz", in its various spellings, was not used by other noted contemporary authors. It may be that this ore was called by the Saxon miners 'Querkluftertz' or the cross-vein-ore. In the Erzgebirge, silver ore is frequently found in small cross veins composed of silica. The name ore (Erz, Ertz) was applied to the metallic minerals, the gangue or to the vein material as a whole. Tomkeieff (1941) suggested an etymology for quartz: "The Saxon miners called large veins - Gänge, and the small cross veins or stringers - Querklüfte. Agricola used the spelling "quarzum" (Agricola 1530) as well as "querze", but Agricola also referred to "crystallum", "silicum", "silex", and silice". The earliest printed use of "querz" was anonymously published in 1505, but attributed to a physician in Freiberg, Germany, Ulrich Rülein von Kalbe (a.k.a. The root words κρύοσ signifying ice cold and στέλλειυ to contract (or solidify) suggest the ancient belief that kristallos was permanently solidified ice. The varietal names, rock crystal and bergcrystal, preserve the ancient usage. The most ancient name known is recorded by Theophrastus in about 300-325 BCE, κρύσταλλος or kristallos. Quartz has been known and appreciated since pre-historic times.
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