I'm doing some research on a potential fraud and he used the term Apache Tears. This is from Wikipedia:
Apache tears are rounded nodules of obsidian (volcanic black glass) with diameter from about 0.5 to 5 cm. An Apache tear looks opaque by reflected light, but translucent when held up to light[1][2]. Apache tears are usually black, but can range from black to red to brown. They are often found embedded in a greyish-white perlite matrix[1][2].
An Apache tear
The name "Apache tear" comes from a legend of the Apache tribe: about 75 Apaches and the US Cavalry fought on a mountain overlooking what is now Superior, Arizona in the 1870s. Facing defeat, the outnumbered Apache warriors rode their horses off the mountain to their deaths rather than be killed. The wives and families of the warriors cried when they heard of the tragedy; their tears turned into stone on hitting the ground.
American singer songwriter Johnny Cash wrote lyrics entitled Apache Tears for his album Bitter Tears (Ballads Of The American Indian).