Search results
Results from the WOW.Com Content Network
Any crystal section can in principle produce an interference pattern. However, in practice, only a few different crystallographic orientations are both 1. convenient to identify, to allow a figure to be produced, and 2. able to produce reliable information about crystal properties.
This sets it apart from rock crystal, amethyst, citrine, and the other varieties of crystalline quartz. Other members of the cryptocrystalline silica family include agate , carnelian , and onyx . Unlike many non-transparent silica minerals, it is the color of chrysoprase, rather than any pattern of markings, that makes it desirable.
Another type of mark is found on glass baskets. Where the glass handles of the baskets are attached to the base of the basket a stamp is made. [9] Each handler had a specific pattern to help identify which handler attached the handle. [9] The marks began in the 1950s and were instituted by Frank M. and Bill Fenton. [9]
The way a mineral splits (or “cleaves”), particularly along planes in the crystal structure. Cleavage is generally described by. how well a mineral can be split to produce a flat plane, a process controlled by planes of weakness in the crystal structure. the number of distinct directions of these cleavage planes; the angles between those ...
Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. [1] Lead glass contains typically 18–40% (by mass) lead(II) oxide (PbO), while modern lead crystal , historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. [ 2 ]
Westmoreland was known to use primarily two marks on their products. The first mark was a "W" found inside of a Keystone which can be found from the period of 1910 through the mid 1940s. The second mark, which is the more commonly known by collectors and dealers, is the intertwined W and G that Westmoreland began to use in 1946 on most of the ...
Asterism is generated by reflections of light from twin-lamellae or from extremely fine needle-shaped acicular inclusions within the stone's crystal structure. [1] A common cause is oriented sub-microscopic crystals of rutile within the gem mineral. It occurs in rubies, sapphires, garnet, diopside, and spinel when a cabochon is cut from a ...
Tyrone Crystal acquired Tipperary Crystal in 2000 as part of an investment plan that spent £500,000 on a new visitors' centre that opened in 2001. [2] The company was acquired by businessmen Peter Maginnis and Nigel Blackburn in 2006. From 2005, Tyrone Crystal manufactured the trophy for the Canadian Grand Prix. [3]