This standard specifies the terms and definitions, testing methods, item selection and testing characters of gems.
This standard is applicable to gems testing.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 16552 Gems - Nomenclature
3 Terms and definitions
For the purpose of this standard, the terms and definitions specified in GB/T 16552 as well as the followings apply.
3.1
crystal
solid with a lattice structure, of which, the internal particles are regularly arranged in a regular periodic arrangement in space
3.2
crystalline
crystalline solid (crystal)
3.3
crystalline aggregate
block composed of numerous crystallines
Note: crystalline aggregate includes phanerocrystalline aggregate and cryptocrystalline aggregate.
3.4
non-crystalline
solid of non-lattice structure, of which, the internal particles are irregularly arranged in space
3.5
crystal system
classification reflecting the symmetry of the crystal, which is divided into seven crystal systems according to the symmetry degree: equiaxial system, hexagonal system, tetragonal system, trigonal system, orthorhombic system, monoclinic system, and triclinic system
3.6
crystal habit
habit of certain mineral of tending to crystallize into a certain form under certain external conditions
3.7
crystal twinning
regular formation of two or more of the same crystals according to certain symmetry rule
Note: it is classified into contact crystal twinning, interpenetrant crystal twinning and ring crystal twinning according to the individual formation mode of crystal twinning. The contact crystal twinning is further classified into simple contact crystal twinning and polysynthetic crystal twinning.
3.8
twinning striation
linear striation appearing on the crystal face, cleavage plane or gems cutting plane of crystal twinning joint surface
3.9
crystal face
plane encircling the crystal surface, which is naturally formed during crystal growth
3.10
striation
straight striation formed by a series of so-called adjacent faces on a crystal face, also called growth striation or combination striation
3.11
color band
uneven distribution of internal color in a band (or block) shape
Note: the original color band is a change in color depth or color due to changes in medium composition and growth environment during crystal growth.
3.12
optic character
phenomena generated due to the action of material in the incidence and propagation directions of light, including such characters as the isotropy and anisotropy of material, axiality and positive/negative characters of anisotropic material
3.13
isotropic material
material with optic character the same in all directions
GB/T 16553-2017 The following standards are cited：
