([Click here to download a PDF of this document](https://www.slee.com/assets/CrystalEdge%20GenInfo%20-%20Crystal%20or%20Glass.pdf)) # Is it Crystal or is it Glass? --- ### What is Crystal and what is Glass? Technically the difference is determined by a “REFRACTIVE INDEX” scale. This scale determines the clarity level of a product? Crystal (depending on the quality) has a relatively high refractive index whereas glass has a lower value. A high index reading (of above 1.5) is generally considered crystal and below this it is glass. The refractive index scale determines the clarity of any clear material by its ability to transmit light through it, or deflect light traveling at it, at the speed of light. Glass generally has a refractive index of 1.46 or lower and Optic Crystal is 1.52 and higher. By comparison a cut diamond has an index of 2.42. Now for the **non-technical** version. ### Crystal Crystal is produced in two basic types, soft and hard. Soft crystal is known universally as lead crystal. Lead oxide of up to 35% is added to this crystal to soften it, and to allow it to be formed, blown or molded easily. The lead oxide also gives the crystal a beautiful sparkle. It is easy to grind and polish patterns with. Full lead crystal must have at least a 24% lead oxide content to use this name. Lead crystal is most commonly used for bowls vases and molded shapes. It is a very clear product. Hard crystal is used primarily for optical requirements. It is commonly called Optic Crystal but it’s true name is Opthalmic Crystal or Crown Glass. Its hardness and high clarity makes it ideal for producing telescope and camera lenses. In 1996 Optic Crystal (made only in the US and Europe) was first introduced commercially to the award and recognition industry, but with limited success due to the very high cost. Not long after this China started producing less expensive versions of Optic Crystal known today as K9. Today almost all Optic Crystal products are made from K9, however the quality of this crystal varies widely. The higher the cost the better the quality will be. At the lower end of the cost range K9 crystal will have no UV (ultra violet) light resistance and will turn yellow if exposed to any UV light. ### Glass Glass is an extremely hard material that is very commonly used in the trophy, award and recognition industries. Known as flat glass it is available with a green tint, referred to as Jade Glass, or in a clear glass with a slight blue tint, known as Crystal Clear Glass. Glass with other tints (gray, bronze, black & blue) are also available. Jade Glass gets its green tint from an iron ore content that is inherent in the silica sand that is used to produce flat glass. Crystal Clear glass (also known as low iron glass) uses a more pure silica sand that has virtually no iron ore content. It is also a very hard glass. Premium quality Crystal Clear glass is almost a clear as Optic Crystal, but it is not actually crystal. Some of the brand names for this type of glass are Starphire® Diamant® Krystal Klear® Optiwhite® and Vitroluz™. Crystal Clear glass is a preferred product for etching and color filling applications as its clarity is excellent at a reasonable price.