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.
Gems are silicates which can be very stable, hard minerals. Like gemstones, one of the characteristics of a precious metal is its rarity. A few gems are oxides and only one gem, diamond, is composed of a single element, carbon. Often, new names will be created for ordinary sounding minerals which sound prettier or more valuable, such as Moldavite for the green variety of tektites.
It could not be "precious" if it were common! This means that the metal must be malleable, that it can be bent, hammered, or otherwise shaped. Two other characteristics are also important. There are also many gemstones that are not true minerals, but which are gemstone varieties of recognized minerals.
Gemstones are so durable
A few are mineraloids not true minerals and are including here: opal, amber, and moldavite. Foremost is durability - it must not easily corrode away, nor can it be brittle. It is so durable that nearly all of the gold ever mined is still in circulation or storage. In some cases, the names are true misnomers, such as Green Amethyst for prasiolite-a transparent green variety of quartz.
In most cases, these variety names are historical, as the gemstones were not recognized as being varieties of other minerals until well after the name was in common use such as aquamarine, emerald, and heliodor as varieties of beryl. And that is related to the third characteristic, ductility. You can see the options are endless and when you are commissioning a piece, why compromise a thing when you can choose!