Obsidian is glass that has sometimes formed naturally when lightning strikes in sand. But Obsidian is generally from volcanic lava which cooled too quickly for significant crystallization to occur. Although most often black, Obsidian does present in colors such as brown and gray, and less likely but still possible blue, red, and green. These colors maybe be uniform, banded, or even spotted in an Obsidian. The coloring is caused by the presence of iron, manganese, or titanium, and the levels at which those are present. Obsidian is often the result of volcanic lava coming in contact with water (a lake or an ocean), and thus being cooled too quickly to form a clear crystalline structure. The process does produce a glassy texture in the resulting rock. Obsidian is found in areas where volcanic activity is, or has been in the past. Many locations including Hawaii, Japan, Iceland, Hungary, Mexico, Ecuador, and Guatemala.