You may put a dull or matte finsih on metal to lessen reflection but
then the photo is not the same item you have later when polished to a
shine. To be honest to the object photographed, try to control
reflection with first diffused light and creative angles of the photo
or object, disguise reflections by controlling what is reflected and
how strongly by placing objects such as a virtical tube (or two) of
white paper in the area of the subject, viewing in the viewfinder and
moving the subject, lights and paper objects to find the best
combination. The paper tubes or shapes can provide an unidentified
and uniform reflection which works find in a photo and helps avoid
the killer “black” sections of reflection on shiny metal.
Jewelry photography is not easy. A flat bed scanner will work
surprisingly well with flat objects but most require the light tent
or other diffuser.
For smallish things I have used a dull white plastic tea pitcher
with a hole in the bottom for the lens to view through, sanded
plastic to increase diffusion and lights placed outside the pitcher.
That is rock bottom do-it yourself.
Remember also, if used creatively, a bit of reflection will add spif
to a straight forward technical shot. If stones are involved and you
have the software to do it, photograph the item in good point source
light to get the stones, while keeping the camera in the same
position for the diffused lit shots, then with graphics software cut
the stones and layer on the diffusedlit photo.
Best Wishes with the photos. Tom