Does not display a "play of color". Incident light passing into or through this material emanating from the amorphous mass as random oriented white light. This is Opal the mineral (common opal) which has only a nominal value. When common opal occurs in a clear (transparent) form which is often used for cutting "facetted" gemstones. This material is often referred to as 'jelly opal or fire opal'; but when it shows a play of color it is referred to as 'crystal opal' and is then classified as Precious Opal.

Opal Resources Canada Inc. is developing product lines to use all of the various types of opal found in our deposit.

Occasionally, opal formation conditions are such that the "micro-spheres" of silica precipitate in uniform sizes and orderly orientation. When this happens the white incident light which enters the opal is diffracted by the orderly spheres into the colors of the rainbow as it emanates from the amorphous opal mass. The play of color is therefore an optical rather than a chemical property. This play of color is the sole distinguishing feature between common opal and precious opal.

The sketch above illustrates what a natural solid opal is. Essentially, it is a cut or rough solid opal with no backing or overlay. These are cut from the larger more competent pieces of precious opal. Smaller pieces and chips of opal are used in inlay jewellery. A cut solid opal is referred to as a Cabochon.

The sketch above illustrates what a natural boulder opal is. These are cut from the more competent pieces of opal bearing rock utilizing the natural rock as part of the body of the stone. Essentially, it is an opal utilizing the natural rock as a backing.