is a trade name given to a particular type of obsidian. There is a story regarding this name and here is what I found in Vikipedia:
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. 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. In the 1950s Apache tears could easily be found on the Arizona desert - near main highways.
The Apache tears originate from obsidian lava flows or lava domes. If water is present during cooling of the obsidian lava, the obsidian may hydrate (i.e., water enters the obsidian glass converting it to perlite). Curved, onion-like fractures may form. If the central core does not get hydrated, that fresh obsidian core ends up being the Apache tear.
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 upon hitting the ground.
The nodules appear black ,but when we look against a source of light is often transparent of a dark brown color, and in some cases like in this gem here are color change at incandescent ligth.
From Arizona desert.