Defining the difference between crystal and glass is not an exact process. While is it true that all crystal is also glass, only certain types can be properly identified with this term. Outside this rather broad statement, however, there are not any ironclad rules that are universally invoked as part of the defining process. Across the globe, there are different standards that are employed in various countries around the world that determine if the quality and lead content of a particular substance can be properly classified as crystal or not. Even within some countries, the qualities that must be present in order for glass to earn the other name may vary.
The lead content of glass is usually a determinant in the classification of finished goods. In the European community, items that have more than 4% but less than 10% of lead monoxide usually earn the designation of glass. While this is not always the case, items that are found to have a lead content of 8 to 10% is granted the status of lead glass. Goods with a lead monoxide content of between 10% and 30% earn the designation of crystal. In the event that the lead monoxide content exceeds 30%, the item is often identified as lead crystal.
In the United States, a lead monoxide content of 1% is sufficient for an item to be classified as crystal. In other countries around the world that do not adhere strictly to the standards used by the European community, the range of lead content required before glass can be identified with this term may range from anywhere between 3% to 15%. Items with a higher lead monoxide content would be classified as lead crystal.
Both, when molten, can be used to create beautiful and somewhat fragile pieces. Among the items constructed in this way are holiday ornaments, decorative figurines, delicate picture frames, and other items that are crafted with a great deal of detail. Crystal in all forms is considered to be especially desirable when it comes to dishware and drinking wear, as well as carefully crafted flower vases.