ways to protect functional features of your jewelry are as a utility patent (not a design patent) or to maintain the process as a trade secret (which seems like a challenge).
Utility patents. There are several patents for inventions involving magnets and jewelry. Here's a 2012 patent (Patent No. 8,209,824) for a magnetic clasp. Here's a 2003 patent (Patent No. 6,594,87) that provides for magnetic arrangement of jewelry elements. If you want to pursue a utility patent, your first step is to review the prior art for patents such as these and determine whether (1) your invention infringes any valid patents, and if not whether (2) your invention is novel and nonobvious. The second step is to determine whether your invention is commercial -- are the potential profits worth the potential patent costs? Also, keep in mind that a patent will take approximately two years to obtain and during that pendency period you can't stop those who copy the invention.