Obsidian can refer to two very different things: a naturally occurring volcanic glass or a personal knowledge base/note-taking application.
🌋 Obsidian (Volcanic Glass)
Obsidian is an extrusive igneous rock that forms as a natural glass.
Formation: It's created when felsic lava (rich in silica) erupts from a volcano and cools very rapidly with minimal crystal growth.2 This quick cooling prevents atoms from arranging themselves into a crystalline structure, which is why it forms a glass.3
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Appearance and Properties:
It is typically jet-black, but impurities can cause colors like brown, green, or even red.
4 Varieties like Snowflake Obsidian (with white cristobalite crystals) and Rainbow Obsidian (with an iridescent sheen) are also common.5 It has a glassy (vitreous) luster and breaks with a distinctive conchoidal fracture (smooth, curved breaks).
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Uses:
The edges formed by conchoidal fracture are extremely sharp, sometimes sharper than surgical steel.
7 Historically, ancient civilizations (like the Aztecs) used obsidian extensively for making cutting tools, weapons (arrowheads, knives), and mirrors.8 Today, it is still used for specialized surgical scalpels, as a semiprecious gemstone for jewelry, and in decorative landscaping.
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💻 Obsidian (Software)
Obsidian is also the name of a popular, free, and flexible personal knowledge management (PKM) and note-taking application.
Function: It is designed to help users organize, link, and structure their thoughts and knowledge.
11 It operates on a local folder of plain text Markdown files (called a "vault"), meaning your data is stored on your device and not locked into the application itself.12 Key Feature: The software's main draw is the ability to create internal links between notes, forming a visible "web" of knowledge.
13 These connections can be visualized using an interactive Graph View, which helps users see relationships and structure their thinking in a non-linear way.14 Customization: Obsidian is highly customizable through various core plugins and community plugins (which add features like calendars, Kanban boards, and more) and themes.
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