Made this piece a month ago. I was very interested in creating in 3d some realistic gems or minerals. So, I decided to render a Labradorite necklace. Why this mineral? I think it's very beautiful and very complex. It was really a challenge, material setup was very complex, but I went pretty easy on lights - just HDRI and a few area lamps. A little bit of color correction in Photoshop, no other detail added. Rendered in Blender 2.8 Cycles, tested lights and materials in EEVEE first.
Oh, by the way, very important detail - this work inspired me the most, so the most of the design of this necklace I got from this real necklace (https://www.deviantart.com/dark-lioncourt/art/Northern-Lights-necklace-454084677).
Thank you for your attention and have a good day! :)