Smoky Quartz is a grey and translucent variety of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. Like other quartz gems, it is a silicon dioxide crystal. It was not commonly used in the ancient times, but it has recently become a popular gemstone used for jewelry.
Imitation Rhodium uses a similar-looking material to substitute for rhodium. It makes the jewelry more affordable, but at the same time keeps the same appearance and quality as a rhodium coating.