Thank you Jack for your comment. Yes you are right, in that situation it is still possible with a black background because it is not blackish enough 😉
Especially with tiny real black and somehow opaque objects with less refections at the surface it will be very hard to distinguish between the fossil and the background. In these cases a dark grey background is your only chance to get good images. The image of your recently uploaded graptolite is very nice btw.
Thank you for that. We need more such high quality images.