I don't recognize either strand to be typical howlite nor magnesite. Howlite typically has a wispy gray matrix. (These are not "synthetics," but are imitations.) Without suggesting they are authentic, I'd say they look OK. It can be very difficult to identify bead materials from a few photos. The dark matrix is a bit unexpected. It's very dark.

Perhaps Danny will take a look and give an opinion.

Good luck. Jamey