(Assuming you have a single lense reflex camera) Use diffused natural light with "daylight film" - slower ASA for good natural color and saturation. This avoids all the color shift problems and expense of artificial lights and filters. Reflect light with mirrors and white paper to fill in shadows. diffuse direct sunlight with white milky plexiglass, tissue paper, or a cloth "tent" made with a T-shirt to prevent burned out specular (brilliant) reflections. To float an object in space - place it on frosted glass and reflect light from beneath. Close the lense aperture to the smallest hole (highest number). Use a "neutral gray card" with your meter to set the long exposure times. To prevent camera shake: Use a solid tripod, lock the mirror up (if you can), use a shutter cable and/or the delay feature - stand still. And a really neat trick: To brighten a dull stone without adding too much light for the metal - make an opaque slide with a pin hole to fit into a slide projector. use the projector with another tripod to aim a tiny beam of bright light into just the stone.