What is the antonym of rhinestone?

There isn't a single perfect antonym for "rhinestone." It depends on what aspect of the word you're trying to contrast. Here are some options and the context they fit in:

* For material:

* Diamond: A real, precious stone, as opposed to the imitation rhinestone.

* Gemstone: Any natural, precious or semi-precious stone, again contrasting with the imitation nature of rhinestone.

* For appearance:

* Plain: A simple, unadorned surface without any sparkle or embellishment.

* Matte: A dull, non-reflective finish, opposite to the shiny, sparkling nature of rhinestone.

* For value:

* Cheap: Emphasizing the low cost and artificiality of rhinestone.

* Simple: A straightforward, unadorned design, contrasting the flashy appearance of rhinestone.

Ultimately, the best antonym depends on the specific situation and what aspect of "rhinestone" you are trying to oppose.