Physical Characteristics of Obsidian: Unique Colors and Shapes

Obsidian, a natural stone with fascinating hues, is most commonly black but can also appear in shades of brown, green, or purple. Occasionally, it can display hues of blue, red, orange, or yellow, offering an infinite variety of dynamics and nuances. These color variations stem from impurities and oxidation changes of chemical elements present in the stone. Rich in magnesium and iron, obsidian showcases a unique surface, composed of naturally formed streaked, speckled, or striped patterns.

Some specimens may even exhibit a blend of two different colors. Obsidian can also showcase an iridescent or metallic aspect, resulting from the light reflection of tiny inclusions of mineral crystals, rocky debris, or gas.

The golden and silver varieties of obsidian are particularly sought after for jewelry making. Among the rarest obsidians is the Manto Huichol obsidian, also known as Mentogochol.

**Obsidian: Origin and Composition**

Obsidian, a natural glass, forms during a volcanic eruption rich in silica and low in water (less than 3%). Its rapid cooling results from its quick ascent from the depths, freezing the crystallization mechanisms. This rapid formation prevents atoms from organizing into crystalline structures, resulting in black volcanic glass with sharp edges and fine blades. Composed mainly of silicon dioxide (SiO2) at over 70%, it exhibits a conchoidal fracture and a hardness of 7 to 7.5 on the Mohs scale, allowing it to scratch glass.