I've read and learned that the older Sterling jewelry had more Nickel metal in it which is magnetic. Old Sterling will "barely" be attracted to a strong magnet and the attraction is very weak. If your necklace is gold over silver, Vermeil jewelry, and it's over older Sterling Silver, the slight attraction that even less than the attraction of the spring closure, would be seen.
Your post made me smile! How you are doing with finds without your detector is what I've done, too. In fact, when an older elementary school was being remodeled and re-roofed, I met the job site foreman one afternoon when my battery pack went dead. I ended up getting almost a full pallet of (30) sacks of Cement the brick masons wouldn't come get, several solid core doors, electrical conduit, and an enclosed U-Haul trailer's worth of 6" thick, foil faced Owens-Corning fiberglass insulation for free. The high school also was re-roofing their campus and having trouble finding those big long commercial metal dumpsters. So, I rented another $35 a day U-Haul trailer and hauled home over 150 foam-laminated sheets of 1-1/2" thick, 4x8 ft. sheets of insulation. My workshop has 6" of foam and 6" of fiberglass insulation on the hot West side and cold North side that would cost over $700.00 at the Box Stores.
You'll keep finding all sorts of things, and meet people, by keeping up what you are doing!!