The opal here formed as nodules of silica that filled pockets in a volcanic material similar to Obsidian.  Most of the opal has no fire and is called common opal.  The fire layers tend to be thin, relatively flat layers in these nodules.  A very small amount of opal is found here that will cut solid stones.  Nearly all the fire opal must be cut into triplets.  Normally this involves a clear top layer and a black bottom layer with a thin slice of opal in the middle.  All our Spencer opal are triplets unless we specify otherwise.

As in most mining operations, there is a lot of marginal quality material worked for each really good stone that is available.  We have no time or desire to work low quality stones.  What we cut or buy represents the upper 5 to 10% of  the available material.