This pendant consists of a spiral drawn with Turtle Tina and a hollow spherical eyelet created using PLaSM. Click on the 3D model to view the source code. You can also run the model, and adjust it to your needs. The code is extremely intuitive, so I am sure that you will figure it out! You can use the Export menu to save it as an STL file for 3D printing. First the 3D model:
And here is the corresponding 3D print:
