Obsidian Chain

Lore & Background

Obsidian is a mineraloid rather than a true mineral because it lacks a crystalline structure. It forms when viscous felsic lava cools quickly at the edges of flows, domes, or during contact with water and air, inhibiting atom diffusion and nucleation. This rapid cooling traps atoms in place, creating a natural glass rich in silicon dioxide (over 70% by weight), along with aluminum, iron, potassium, sodium, and calcium oxides. Obsidian older than the Miocene is rare because it devitrifies into fine-grained mineral crystals over time, though exceptions exist like Cretaceous welded tuffs. Its color varies from black to brown due to magnetite nanoinclusions or transition elements, with specific patterns like snowflake (cristobalite spherulites) or fire sheen caused by thin-film interference.

In Their Own Story

Historical usage of obsidian dates back to the Acheulian age in Kariandusi, Kenya, around 700,000 BC, where it was used for tools despite being rare compared to Neolithic finds. By the late Neolithic, sophisticated bladelets were manufactured at Lipari and traded as far as Sicily and Croatia. In central Anatolia, obsidian from Acıgöl and Göllü Dağ served prehistoric Near East cultures, while in the Levant, it was used from 12,500 BC onward. Tell Brak, an early Mesopotamian urban center, yielded common artifacts from the late fifth millennium BC. In Europe, obsidian appeared in the Middle Paleolithic and became common by the Upper Paleolithic, with sources like Milos supplying Greece and Hungary/Slovakia supplying the Starčevo–Körös–Criș culture. In the Americas, indigenous groups traded Yellowstone obsidian over 1,500 miles to Hopewell sites in Ohio.

Reader's Guide

To identify or utilize obsidian based on this source, one must look for volcanic locations with rhyolitic eruptions. It is found in Argentina, Armenia, Australia, Chile, Iceland, Japan, Mexico, and the western United States (including Newberry Volcano and Yellowstone). The material is characterized by a conchoidal fracture that produces extremely sharp edges, making it suitable for cutting tools, piercing instruments, and experimental surgical scalpel blades. Its low water content (under 1%) increases upon exposure to groundwater, forming perlite. For dating artifacts, archaeologists use obsidian hydration dating, which measures the rate of water absorption. X-ray fluorescence helps trace origins by matching minor element compositions in artifacts to geological samples from specific volcanoes.

Did You Know?

• Obsidian is not a true mineral because it is amorphous glass with no crystal structure and variable composition.
• Fire obsidian gets its iridescent rainbow sheen from inclusions of magnetite nanoparticles creating thin-film interference.
• Obsidian older than the Miocene age is rare because the glass naturally devitrifies into fine-grained crystals over time.
• A specific type of 'snowflake obsidian' contains white, radially clustered cristobalite crystals within the black glass.
• Ancient Egyptians imported obsidian from the eastern Mediterranean and southern Red Sea regions for tools and decorative objects.