Effect exhibited on some minerals (usually only in polished cabochons) causing it to reflect a billowy, star-like formation of concentrated light which moves around when the mineral is rotated. Asterism is caused by dense inclusions of tiny, parallel, slender, fibers in the mineral which cause the light to reflect in such an interesting manner. Minerals that display asterism may exhibit four, six, and sometimes twelve rayed "stars", depending on the inclusions, size, and facet mode. Some specimens may display much stronger asterism than others, and some specimens may have areas where the inclusions are not present, leaving holes or empty areas in the star.
Asterisms are sub- or supersets of constellations which build a constellation itself, or a group of stars, physically related or not. Best known is the Big Dipper as a part of the Great Bear. But there are more than just this one. Click here for a table of asterisms.
A "star" or pattern of rays, typically six rays, crossing in a single spot on a cabochon cut gemstone when viewed under a single source of light. Star Sapphire is one of the best-known examples of a gemstone that exhibits the phenomenon known as an asterism.
A pattern of stars that is not an official constellation but appear within a constellation. Two example’s are the “Big Dipper” which is a portion of the constellation Ursa Major and the three prominent stars which form “Orion’s Belt” within the constellation of Orion.
A luminous star like effect exhibited in some gemstones like star sapphires, garnets and rubies. asterismAsterism is caused by inclusions of tiny, parallel, rutile needles and may result in four, six or even twelve rayed stars. (Pronounced: as-ter-iz-mm)
It is the effect which is exhibited on some minerals, generally in polished cabochons only, and causes it to reflect a billowy, star-like formation of concentrated light that moves around when the mineral is rotated. It is caused by the dense inclusions of tiny, parallel, slender, fibers in the mineral that cause the light to reflect in an interesting manner. Minerals which display the asterism may exhibit four, six, and sometimes twelve rayed stars, depending on the inclusions size and facet mode. Some specimens displays stronger asterism than others and some have areas where the inclusions are not present.
A special grouping of stars that are part of a constellation. These stars form recognizable figures in the sky. An example would be the Big Dipper. It is made up of stars in the constellation of Ursa Major also known as the Great Bear, but there are more stars in that constellation that are not part of the Big Dipper.
A recognizable grouping of stars which is a subset of a Constellation. For Example: 'The Big Dipper' is an asterism of the Constellation Ursa Major (The Big Bear) or 'Pleiades' is an asterism in the Constellation Taurus (The Bull).
A group of stars in a recognizable pattern that people commonly associate with each other, such as the Big Dipper or the Square of Pegasus. An asterism can be part of a formal constellation, or it can be formed from the stars of several constellations.
A group of relatively bright stars forming an easily-recognized pattern. Not constellations as such, asterisms often form part of constellations (such as the Big Dipper in the larger constellation of Ursa Major, the Great Bear), or encompass stars from more than one constellation (such as the Summer Triangle which consists of the brightest stars from three different constellations, Cygnus the Swan, Lyra the Harp, and Aquila the Eagle).
Also know as the star effect, this is a reflection effect that appears as two or more intersecting bands of light across the surface of a gem. It is usually created through reflection of light by thin fibrous or needle-like inclusions that lie in various directions. There are 6 ray, 4 ray and, rarely, 12 ray stars. Ruby and Sapphire cabochons can sometimes very effectively show this phenomenon.
In astronomy, an asterism is a pattern of stars seen in Earth's sky which is not an official constellation. Like constellations, they are composed of stars which, while they are in the same general direction, are not physically related, often being at significantly different distances from Earth. An asterism may be composed of stars from one or more constellations.
In typography, an asterism is a rarely used symbol consisting of three asterisks placed in a triangle, used to call attention to a passage or to separate sub-chapters in a book. It is Unicode character U+2042: .