5 Kinds of Glass Made by Nature | Summary and Q&A

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September 15, 2019
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5 Kinds of Glass Made by Nature

TL;DR

Natural silica glass, such as obsidian and opals, can be found in various forms and colors due to impurities and molecular structures. Glass can also be formed through meteorite impacts, lightning strikes, and even by living organisms.

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Questions & Answers

Q: How is obsidian formed and why is it mostly black?

Obsidian is formed from thick volcanic magma high in silica content. It cools quickly underground or on the surface, preventing the molecular arrangement into crystals. The presence of microscopic impurities gives obsidian its black color.

Q: What gives opals their vibrant colors?

Opals get their colors through a phenomenon called play of color, where silica spheres and cement bend light differently. The size of the spheres determines the colors seen, ranging from violet to red.

Q: What is the origin of tektites and how are they formed?

Tektites are formed during meteorite impacts on sandy or rocky ground. The impact heats up and melts the surrounding ground, creating molten blobs that cool into glass while descending back to Earth.

Q: How are fulgurites formed when lightning strikes sand?

When lightning strikes wet sand, it raises the temperature to 1800 degrees Celsius, melting the surrounding silica sand. The resulting fulgurites are usually tan or black, but variations can occur depending on impurities present.

Q: How do glass sponges create glass-based skeletons and what are their unique features?

Glass sponges, like the Venus flower basket, have amorphous silica spicules that fuse together after the sponge dies, forming a glass-based skeleton. These skeletons can transmit light like fiber optics and have braces that make them less brittle.

Summary & Key Takeaways

  • Natural silica glass, like obsidian, is formed from thick volcanic magma rich in silica and cools quickly to create an amorphous molecular structure.

  • Opals are colorful gemstones made up of silica spheres and cement that diffract light, creating a play of color effect.

  • Tektites are glass formations created during meteorite impacts and can be found in specific areas on Earth's surface.

  • Fulgurites are formed when lightning strikes wet sand or silica-based rocks, creating hollow tubes or non-tube-shaped glass formations.

  • Glass sponges, like the Venus flower basket, have amorphous silica-based structures that form after the sponge dies, and their spicules can transmit light like fiber optics.

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