|
Process of Casting silver Jewellery
A two-step process, investment casting, produces small, complex shapes. Most castings, especially large ones, are made in sand molds. Permanent metal molds are used to make many small, simple parts; shell molding gives greater accuracy for a large volume of semi precision parts.Molten silver is poured into the cavity and allowed to solidify. Sand, mixed with a binder to hold it together, is pressed around a wooden pattern that leaves a cavity in the sand. Wax or plastic replicas of the parts are molded in accurate metal molds. Top of the line casting equipments are utilized to produce the silver jewellery. When the whole mold is heated, the replica melts, leaving behind a cavity into which silver is poured.
Gemstones are identified by gemologists
Gemstones are identified by gemologists. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction. Who describe gems and their characteristics using technical terminology specific to the field of gemology.Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. They may have luminescence and a distinctive absorption spectrum. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al2O3). Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.
All gemstones have some characteristics
Many gemstones are used in even the most expensive jewellery depending on the brand name of the designer, fashion trends, market supply, treatments etc. Others are too common and are given a semi-precious status. Most gemstones have good hardness and a high index of refraction.All gemstones have some characteristics falling short of perfection though; even the seemingly perfect Diamond has four directions of cleavage. Since quartz is everywhere especially in common dirt and dust. Any material that is softer may be scratched during ordinary wear. Nevertheless, diamonds, rubies, sapphires and emeralds still have a reputation that exceeds those of other gemstones.
|
