In regard to Gemstones, What Do These Terms Mean?
Natural stones are mined from the earth, polished, and possibly treated with heat or irradiation to bring out their final form.
This is a term that tricky advertisers use in lieu of the term natural. Genuine gemstones can actually be lab-created, and often are.
Manmade stones that are the exact composition as their natural, earth-mined counterparts but are created in a lab at significantly less cost. These stones are often more "perfect" than the real stones.
"Stones" made of glass, quartz or plastic.
"Stones" comprised of layers of material, one or more of which may be the real stone such as quartz, or opal. Peacock quartz is a doublet made of real quartz with a man-made color-layer or glue that gives it the beautiful caribbean sea color. Some sellers sell opals that are doublets with a small sliver of opal attached to a different backing.