Apache Tear drop is a form of black obsidian. It is found in Arizona and other parts of the US. It is composed of feldspar, hornblend, biotite, and quartz. It is a form of volcanic glass formed by crystallization. 
 
The Apache tear drop legend
After the Pinal Apaches had made several raids on a settlement in Arizona, the military regulars and some volunteers trailed the tracks of the stolen cattle and waited for dawn to attack the Apaches. The Apaches, confident in the safety of their location, were surprised and out-numbered in the attack. Nearly 50 of the band of 75 Apaches were killed in the first volley of shots. The rest of the tribe retreated to the cliff’s edge and chose death by leaping over the edge rather than die at the hands of the white men.
 
For years afterward those who ventured up the treacherous face of Big Picacho in Arizona found skeletons, or could see the bleached bones wedged in the crevices of the side of the cliff. 
 
The Apache women and the loves of those who had died gathered a short distance from the base of the cliff where the sands were white, and for a moon they wept for their dead. They mourned greatly, for they realized that not only had their 75 brave Apache warriors died, but with them had died the great fighting spirit of the Pinal Apaches. 
 
Their sadness was so great, and their burden of sorrow so sincere that the Great Father embedded into black stones the tears of the Apache women who mourned their dead.
 
These black obsidian stones, when held to the light, reveal the translucent tear of the Apache. The stones bring good luck to those possessing them. It is said that whoever owns an Apache tear drop will never have to cry again, for the Apache maidens have shed their tears in place of yours. [Truth about Crystal Healing, Phyllis Galde]