Hi Karen your antique cameo sounds beautiful. The cameo material sounds like it could be Jasperware. This is a hard, fine grained, unglazed, sometimes translucent, stoneware that was introduced in 1764 by Josiah Wedgwood. The body or the surface is stained with metallic oxides in several colors., of which cobalt blue was most commonly used.
If the surface of the cameo appears to be matte looking or "unglazed" and the dominating color is "cobalt blue" these clues will be good indicators. Note that the image is an example for color only, the material looks like it's been GLazed.
