It is known that nepheline is used not only as a raw material for the production of aluminum and as a cement raw material, but also as an ornamental and jewelry stone used to make cabochons from translucent and translucent varieties with an attractive color. Many people know the so-called "solar nepheline" - translucent (up to translucent) nepheline with inclusions that cause adventurism. But rarely has anyone come across transparent colorless nephelines suitable for facet cutting, and there are such stones, but they are extremely rare. Most of the cut nepheline comes from Canada (Ontario) and Germany (Baden-Wurtenberg). The rarity of nepheline is not only its disadvantage, which requires an individual approach to each stone, but also its dignity, elevating it to the category of gemological rarities.
Currently, gemstones are produced by two fundamentally different technological methods - the High Pressure - High Temperature method (“HPHT”, High-pressure & High-temperature) and the Chemical Vapor Deposition (“CVD”, Chemical vapor deposition) method. The "HPHT" method is the most tested classical synthesis method, which can be used both carbon deposition on diamond from flux melts and catalytic reactions. In "CVD" synthesis, diamond growth occurs on a seed during carbon deposition mainly from a gaseous medium at relatively low temperatures and pressures.
Jewelry and precious stones are just such a category of goods, when buying which you need to pay attention to many criteria.