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As the access to materials increased, competition to design the most beautiful patterns rose, with an estimate of over 300 different kogin-zashi patterns being created. In the 20th century, the craft of kogin-zashi was streamlined, establishing the three general types that are seen today: nishi-kogin , higashi-kogin , and mishima-kogin . [ 2 ]
A conoscopic interference pattern or interference figure is a pattern of birefringent colours crossed by dark bands (or isogyres), which can be produced using a geological petrographic microscope for the purposes of mineral identification and investigation of mineral optical and chemical properties.
Each mineral, depending on the orientation, may not exhibit the maximum birefringence. It is important to sample a number of similar minerals in order to get the best value of birefringence. Uniaxial minerals can look isotropic (always extinct) if the mineral is cut perpendicular to the optic axis (this situation can be revealed with the ...
Many sashiko patterns were derived from Chinese designs, but just as many were developed by native Japanese embroiderers; for example, the style known as kogin-zashi, which generally consists of diamond-shaped patterns in horizontal rows, is a distinctive variety of sashiko that was developed in Aomori Prefecture.
In mineralogy, an inclusion is any material trapped inside a mineral during its formation. In gemology , it is an object enclosed within a gemstone or reaching its surface from the interior. [ 1 ] According to James Hutton 's law of inclusions, fragments included in a host rock are older than the host rock itself.
Mineral symbols (text abbreviations) are used to abbreviate mineral groups, subgroups, and species, just as lettered symbols are used for the chemical elements. The first set of commonly used mineral symbols was published in 1983 and covered the common rock-forming minerals using 192 two- or three-lettered symbols. [ 1 ]
Asterism on the surface of a blue star sapphire. A purple-pink star sapphire displaying asterism in a platinum ring.. An asterism (from Ancient Greek ἀστήρ (astḗr) 'star' and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone.
In paleontology, dendritic mineral crystal forms are often mistaken for fossils. These pseudofossils form as naturally occurring fissures in the rock are filled by percolating mineral solutions. They form when water rich in manganese and iron flows along fractures and bedding planes between layers of limestone and other rock types, depositing ...