Opal is a hydrated amorphous form of silica; its water content may range from 3 to 21% by weight but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock. Opal is softer and more easily chipped than most other popular gemstones. It has a hardness of about 5.5 to 6.0 on the Mohs hardness scale.

Pink opal veins are named like this according to the most beautiful color they can have (rose-colored to strong pink). Uniform strong pink colorations like in this picture of a top-quality natural piece of a vein are only used for premium jewelry production and are sold at the mine at up to 1.000,- USD per kilo. Most of these top-quality veins range from 5 – 10 mm in thickness (1/5th to 2/5th of an inch). A 2 cm layer like in the picture is an even greater rarity.

Even the thickest pink opal vein will not surpass 6 cm thickness (2.3 inches). All the pink opal veins with a thickness of 1 cm to 6 cm are almost always mixtures of many colors from white, to the faintest rose colors, to strong pinks, also yellow, black, brown, fleshy colors, and 

many more shades. Finally, they are mixed with matrix rock. Those boulder color mixes are the ones used for “cheaper” ethical pink opal crystals and carvings like hearts, spheres, pyramids, etc. instead of jewelry.

Here is a range of colors you can find in good quality boulder pink opal:

The high demand for pink opal, the low extraction in a handful of small artisan mines, and the lack of knowledge in the typical crystal buyer have led to the sale of very low-grade material. This material has several problems in terms of quality: 

1. It does not have the porcelain-like structure and surface of high-quality pink opal, but is coarse and porous instead. As a result, it is not possible to polish this material well. Even if it sometimes has a strong rose color it will never get to the glassy gloss we like so much in good-quality pink opal.

2. Often, it is mixed with large parts of ugly chalky white or brown matrix material, that does not polish well.

3. The colors of this material are often rather brownish than pinkish and it resembles the look of a yogurt rather than an opal (actually we carvers use the term yogurt for this material when we find it in a rough rock delivery and sort it out to be rejected).

Here are some examples of such low-grade cheap material coming from some of the pink opal mines: 

It should not be necessary to state, but: At Gemrock we are not using such material anymore.