The color of obsidian varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to black color. The inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). It may contain patterns of air bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden (sheen obsidian) or rainbow sheen (rainbow obsidian). Small nuggets of obsidian that have been naturally rounded and smoothed by wind and water are called "Apache tears." Obsidian is relatively soft with a typical hardness of 5 to 5.5. Its specific gravity is approximately 2.6.

Obsidian is commonly used for ornamental purposes, for it possesses the peculiar property of presenting a different appearance according to the manner in which it is cut. When cut in one direction it is of a beautiful jetty black; when cut across another direction it is glistening gray.

Obsidian was highly valued in certain Stone Age cultures because, like flintchalk cliffs, Cape Arkona, Rugen Flint (or flintstone is a hard, sedimentary cryptocrystalline silica rock with a glassy appearance. Flint is usually dark grey, blue, black, or deep brown in colour. It occurs chiefly as nodules and masses in chalks and li, it can be fractured to produce sharp blades or arrow heads. Like all glass and some other types of naturally occurring rocks, obsidian breaks with a characteristic conchoidal fractureA conchoidal fracture is produced when some types of mineral, such as obsidian and flint, are broken. The fracture takes the form of a curved surface, reminiscent of the interior of a shell. This characteristic meant that these minerals were widely used i. It may also have been polished to create early mirrorThis article is about the reflective surfaces. A mirror is a reflective surface that is smooth enough to be able to form an image. The best known example is the plane mirror that most people have at home. In it, a parallel beam of light changes its directs.

In Pre-ColumbianThe term Pre-Columbian is used to refer to the cultures of the New World in the era before significant European influence. While technically referring to the era before Christopher Columbus, in practice the term usually includes indigenous cultures as the Mesoamerican obsidian useObsidian was an important part of the material culture of Pre-Columbian Mesoamerica. Its uses, value, production, trade, sources, and analysis are all important aspects of the study of cultures in this region. Practical and Ritual Obsidian Use Almost no s was extensive and sophisticated with carved and worked obsidian for tools, as well as for decorative objects. Well crafted obsidian blades are capable of having a cutting edge as fine as high quality surgical steel scalpelA scalpel is a very sharp knife used for surgery as well as various arts and crafts. Scalpels can have a fixed blade, or a disposable blade. The blades on scalpels are extremely sharp, merely touching a medical scalpel with bare hands to test it, will cuts. The ancient Mesoamericans also made a type of swordA sword (from Old English sweord akin to Old High German swerd is a bladed weapon, consisting in its most fundamental design of a blade and a handle. The blade is normally of metal and often ground to at least one sharp edge and usually has a pointed tip with obsidian blades mounted in a wooden body.