I want to share a technique I just discovered to make photos of small objects appear with no background (only works with white). The object is placed on white paper in the shadow of another object. Two folded pieces of typing paper are placed in the sunbeam to reflect fill lighting from two sides. In photoshop I use the dodge tool (set for highlights at 43% opacity) to “burn” the white background totally white.
I use levels to adjust the brightness and contrast of the object and usually sharpen with the unsharp mask, too(amount 99%; radius 0.5 pixel, threshold level 1.0).
I discovered this technique by accident when photographing bonsai trees at the the Como Park Conservatory. They had white backdrops that resulted in my auto exposure under exposing the trees. When I used photoshop lighten the trees, the background overexposed to pure white which disappears on a white page. 
For these pictures I placed the object on a white background (typing paper) within the shadow of one of my plants in a sunny window. I am just learning that direct sun is often too contrasty. I propped up another piece of white paper in the sunbeam near it to serve as a source of fill lighting. With photoshop I use the dodge tool set for highlights (43%) to “burn” the backdrop totally white.
I tried halogen flood lights but was not pleased with the color accuracy (see the fluorite photos). I have heard that blue spectrum floodlights are better. The better fluorite pictures were taken outside, one in full sun on a white pillowcase and the other in the shade next to some snow.
