The belt of volcanic rocks in which the Mexican opal occurs extends both north into the western United States, and south through the Central American states into South America. The best known occurrence appears to be that in Honduras. It occurs in an area difficult of access, and there has been no commercial production. According to Leechman, quoting from Bauer, the opal may occur in small cavities, but in some cases occurs in bands or veins, sometimes only partly filled with opal, confirming the deposition from an aqueous medium. At other times the opal may be found impregnating and cementing what was apparently a porous volcanic rock, perhaps a tuff.

Precious opal has been reported from other Central American countries such as Nicaragua and Gautemala, but not in commercial quantities.

Precious opal has been reported from numerous localities in the western part of the United States. It is found in small quantities in volcanic rocks in the far western states, from California through to Washington, but by far the most important occurrence is that of Rainbow Ridge in Virgin Valley, Nevada. As Leechman (R0384) notes

In the Rainbow Ridge mine some cavities may be filled with opal, while adjacent cavities may be empty; small seams yielding very small pieces of opal occur in the rock around the pseudomorphed wood.

The colour of the opal from Rainbow Ridge is often exceptional, and much of it rivals the black opal of Lightning Ridge. H.C. Dake, as quoted by Leechman (R0348) states:

It is an unfortunate fact that a high proportion of the Virgin Valley opal, much of which is otherwise of very high quality, is highly prone to cracking and crazing, so that much of the opal found is sold and retained as uncut specimen material.