Photographic dilemmas

Detail of a flamingo jasper and sterling silver necklace

Botswana agate and sterling silver pendant

I've spent this afternoon attempting to take some photographs for the website with very mixed success!  There is such a thin line between underexposing and overexposing each photograph in an attempt to create a photograph of a quality that can be included in the website.  I just don't seem to have the skills (and it's not just down to the camera) to create photographs of any where near the quality of  those taken by Martin, who has taken many of the photographs that appear on the website.  Test photographs above.  Any comments, ideas or suggestions  gratefully received!