The DinoLite micro camera from Mineralogical Research (MinResCo) is a USB interfaced little camera that has a proven track record of doing a good job photographing minerals. Prices can be as low as $185 for a unit that yields 640x480 images.
Another unit is the Pro Scope. which sells for $629 in a non-wireless basic configuration. (The wireless model is less expensive, but works only with an Apple application on an iPad or some other IOS device.) I have not seen results from this camera, and it looks like something a doctor might use to check places we might not like to talk about, but here it is for your consideration.
Tom's Mineralogy Info / firstname.lastname@example.org