2/28/2024 0 Comments Rainbow lattice feldsparIn the early 2000s, a new variety of red or green gemstone resembling sunstone and known as "Andesine" appeared in the gem market. Andesine controversy Various gem colors of Oregon sunstone Sunstone is also found in Pleistocene basalt flows at Sunstone Knoll in Millard County, Utah. The "orthoclase sunstone" variant has been found near Crown Point and at several other localities in New York, as also at Glen Riddle in Delaware County, Pennsylvania, and at Amelia Courthouse, Amelia County, Virginia. Other locations include near Lake Baikal in Siberia, and several United States localities-notably at Middletown Township, Delaware County, Pennsylvania Plush, Oregon and Statesville, North Carolina. Previously the best-known locality being Tvedestrand, near Arendal, in south Norway, where masses of the sunstone occur embedded in a vein of quartz running through gneiss. The feldspar which usually displays the aventurine appearance is oligoclase, though the effect is sometimes seen in orthoclase: hence two kinds of sunstone are distinguished as "oligoclase sunstone" and "orthoclase sunstone". ![]() The middle part of this crystal sparkles, and usually the color is darkest in the middle and becomes lighter toward the outer edges. The optical effect is called schiller and the color of Oregon Sunstone is due to copper. These inclusions give the stone an appearance something like that of aventurine, hence sunstone is known also as "aventurine-feldspar". The optical effect is due to reflections from inclusions of red copper, hematite, or goethite, in the form of minute scales, which are hexagonal, rhombic, or irregular in shape, and are disposed parallel to the principal cleavage-plane. Properties Physical properties Unpolished sunstone It has been found in Southern Norway, Sweden, various United States localities and on some beaches along the midcoast of South Australia. Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance. Microcline or oligoclase and orthoclase varietyĬolorless, orange, yellow, red, green, blue, brown and copper shiller For other uses, see Sunstone (disambiguation). The effect is produced by alternating layers of two types at a scale near the wavelength of light (approximately 0.5 micron) – this leads to light scattering and interference.For the mineral calcite used in navigation, see Sunstone (medieval). Īs an optical phenomenon, adularescence exists only in the presence of light it is a product of the interaction between light and the internal microstructures of the mineral and not a property of the mineral itself. Only clearly defined bands are referred to as "cat's eyes". When the schiller forms an indistinct band, it is said to display a chatoyant effect. Thus, adularescence occurring in non-adularia gemstones is termed differently – the "girasol effect" and opalescence (for opals only) are two such terms. The schiller is scattered by inclusions and appears hazy non-hazy specimens are specially referred to as "milky". However, due to inclusions in these other stones, the effect is displayed differently. Adularescence appears in numerous other gemstones, notably common opal, rose quartz and agate. ![]() ![]() This effect is most typically produced by adularia, a K-feldspar or orthoclase ( KAlSi 3O 8), from which the name is derived. Though white schiller is the most common, in rarer specimens, orange or blue lusters are produced. The schiller, appearing to move as the stone is turned (or as the light source is moved), gives the impression of lunar light floating on water (accounting for moonstone's name). ![]() The effect of adularescence, also commonly referred to as schiller or shiller, is best described as a milky, bluish luster or glow originating from below the surface of the gemstone. The optical effect is similar to labradorescence and aventurescence. The specimen's diameter is 23 mm (0.91 in).Īdularescence ( / ˌ æ dʒ ə l ə ˈ r ɛ s ən s/ AJ-ə-lə- RES-əns) is an optical phenomenon that is produced in gemstones like moonstone. Milky luster or iridescence originating from below the surface of gemstones Adularescence in a moonstone cabochon, Minas Gerais, Brazil.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |