What it is confused with
Black glass and black onyx. Obsidian breaks with shell-like curved fractures and may show gray "snowflakes" or a rainbow sheen.
Black, sometimes with sheen or snowflake patterning
Obsidian crystal meaning
Obsidian is volcanic glass — silica-rich lava cooled too fast to crystallize, black, sometimes with sheen or snowflake patterning, rated 5–5.5 on the Mohs scale. Traditionally, it is associated with protection, boundaries and honest self-examination — attributed, not demonstrated.
- Mohs hardness
- 5–5.5 about as hard as window glass
- Crystal system
- Amorphous
- Pliny, AD 77
- Book 36.67 as “Obsian stone”
- Main sources today
- Mexico also USA, Iceland
Pliny, Natural History, tr. Bostock and Riley.
Is Obsidian a birthstone?
Not in the monthly list — but it does appear in the older zodiac tradition.
By zodiac sign it belongs to Scorpio.
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Properties
Composition
Volcanic glass — silica-rich lava cooled too fast to crystallize
Hardness (Mohs)
5–5.5
Crystal system
Amorphous
Color
Black, sometimes with sheen or snowflake patterning
Mined in
Mexico, USA, Iceland, Italy, Armenia
Worth knowing
Fractures to an edge only nanometres thick — sharper than surgical steel, and still used in some specialist scalpels.
History
Worked into blades across the ancient world; Aztec ritual knives were obsidian.
Buying
Buying Obsidian: fakes, value and treatments
What decides the price
Inexpensive; snowflake, mahogany and rainbow varieties are the most sought after.
Where it is used
Obsidian blades can be sharper than steel scalpels and have been used in some specialist surgery.
A less familiar fact
Each volcanic source has its own chemical fingerprint, so archaeologists use obsidian tools to trace ancient trade routes.
Practical
Caring for Obsidian
How to clean it
Warm soapy water and a soft cloth. Chips easily — store separately.
How to tell it is real
Obsidian is natural glass, so imitation is a fine distinction. Natural material usually contains tiny gas bubbles and flow banding.
How hard is Obsidian?
Obsidian is volcanic glass and behaves like glass: it breaks into razor-sharp edges and chips easily, so it needs its own pouch and suits pendants better than rings. Among the stones in this reference, the next softer is Fluorite (4) and the next harder Turquoise (5–6).
Obsidian, at 5–5.5, is harder than 6 of the other 42 stones here and softer than 36.
Primary source
What Pliny the Elder wrote about Obsidian
“Among the various kinds of glass, we may also reckon Obsian glass, a substance very similar to the stone which Obsius discovered in Æthiopia. This stone is of a very dark colour, and sometimes transparent; but it is dull to the sight, and reflects, when attached as a mirror to walls, the shadow of the object rather than the image.”
Pliny the Elder, The Natural History, translated by John Bostock and H. T. Riley (London: H. G. Bohn, 1855–57), book 36, chapter 67 — read the original text.
Obsidian takes its name from this passage, after the explorer Pliny calls Obsius — Obsidius in later editions. Who Pliny was and why we quote him →
Traditional associations
Obsidian is traditionally associated with protection, boundaries and honest self-examination. Chakra in crystal practice: Root. Element: Earth.
Questions about Obsidian
What is Obsidian made of?
Volcanic glass — silica-rich lava cooled too fast to crystallize, with no crystal structure (amorphous).
Where does Obsidian come from?
Mexico, USA, Iceland, Italy, Armenia.
Can Obsidian be worn every day?
Not in a ring. At 5–5.5 on the Mohs scale it is better kept for pendants, earrings or display, away from hard surfaces, on which it chips like glass.
Sources
Statements of fact on this page were checked against these sources in October 2026. How we choose and check sources: editorial policy.
Cite this page
AstroHot. “Obsidian Crystal Meaning: Properties, Hardness and Origins.” Accessed October 28, 2026. https://astrohot.com/crystals/gemstones/obsidian/
For Wikipedia
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