I'm just going to echo what everyone else here said... don't forget to photograph with a white background. I find plain white paper towel to be a perfect backdrop.
What a nice find! Is there a story behind the pearl? I am also going to compliment you on your bravery in holding it over your sink...I would have for certain dropped it down the drain. It appears to be an oval shape with nice luster...most are rather dull. I would keep it and wear it as a pendant, or in a little cage and wear it as a charm. It is lovely!