A: Interestingly enough, way back in forever ago, mono-filament (fishing line) was used in some beading designs due to the strength that the cording presented, so the fact that your observation was that of fishing line may not have been too far off!
You would be best in determining how hard you are on your jewelry -- and no, we obviously don't mean that you're subjecting your jewelry to any undue treatment, but consider if you wear this piece regularly and what the design is made of. Hematite is a very heavy gemstone just based on what it is made from (Fe2O3), so you're best best may be that of flexible beading wire in either a 19 or 49 strand variety to increase security and allow for better drape when wearing (the 19 and 49 relate to how many wires are used to make the inner core. It is then secured in place with a nylon sleeve that coats the outside) Answer provided by:  JewelrySupply (2/7/2019)