Hello nerds and geeks my favorite kind of people. The craft is how you your self can make you own gem like from STEVEN UNIVERSE.
I I'm the one who made the first version of this with the plastic gem and the mess so after thinking how I could make it better I did so I hope you like it. : )

Step 1: Materials

For this you will need the color of polymer clay you want to use but I'm using blue,yellow,orange, black, and red.
And what ever kind of gloss you want to use I just had clear fingernail polish.
And you will need something to bake the clay in

Step 2: Making the Gem

For this you are going to take the color of choice and make it into a kind of oval shape or what ever shape you want

Step 3: Making the Out Line

This part is optional but I decided to make a black outline around the gym so to look like something that popping out not inside. I did this by rolling the clay really thin and wrapping it around the gem.

Step 4: Then Bake

You will want to bake this at 350 degrees for 1 minute an 20 seconds

Step 5: Get Glossy

You will want to gloss the baked gem and get something shiny like the picture shows.

Step 6: The Costume

If you want to use this for a costume which is what I did you will want to use some liquid latex or something to attach the gem to the desired area.
I put mine in the place amethyst has hers