kristalThe difference between glass and crystal is in the lead. If there is less than 4% of lead oxide, it’s called glass.
Crystal must contain more than ten percent of lead oxide. If it contains more than 30 percent lead, it is high lead crystal like Swarovski (approximately 32 percent lead). The higher the lead content, the higher the refractive index. It shines more than and has a richer color spectrum. For chandeliers it is ground.

Glass with lead can be toxic, but can also stop X-rays and gamma rays.