Just wanted to let you guys know that my boyfriend sells really gorgeous 3D-printed gems for Steven Universe!
They are super light-weight, can be painted and coated (if desired, they come in color when ordered) and are easily attached for cosplay. I've been using these myself for my SU-cosplays and I can highly recommend them ^^
Top photo is the 3D design and bottom photo are the matte printed versions!
Link to his Shapeways shop;
https://www.shapeways.com/shops/rakemakes