Crystals
Obsidian is volcanic glass, not a mineral, Mohs 5 to 5.5, used for truth, grounding, cutting through. The mineralogy, whether it is safe in water and sunlight, what gets substituted for it, and what a stone can honestly do.
Start with the mineralogy, because most of the bad advice about this stone follows from not knowing it. Obsidian is volcanic glass, not a mineral. On colour: Iron and magnetite dispersed through the glass.
Where it comes from: Mexico, Oregon, Iceland and Armenia. Anywhere silica-rich lava cooled too fast to crystallise.
| Property | Value |
|---|---|
| Mineral species | Volcanic glass, not a mineral |
| Chemical formula | Mostly SiO2 with iron and magnesium |
| Mohs hardness | 5 to 5.5 |
| Crystal system | None. It is amorphous, with no crystal structure at all |
| Chakra | Root |
| Usually linked to | Scorpio and Capricorn, and to Pluto |
Hardness matters more than it sounds. The Mohs scale runs from talc at 1 to diamond at 10, and anything below about 5.5 can be scratched by ordinary window glass or by the quartz dust in everyday grit. At 5 to 5.5, obsidian is soft enough to damage in a pocket with keys or in a bowl with other stones. Keep it separate.
Used for the uncomfortable work: seeing a situation plainly, ending something, facing a pattern. The traditional association with mirrors is literal. Polished obsidian was used as a mirror for thousands of years before glass backing existed.
In the shorthand most shops and books use, it is a Root stone, and the three words attached to it most often are truth, grounding, cutting through.
This is the section that matters, and the one most pages get wrong. Cleansing advice is handed around as though every stone were the same mineral, and it is not. Here is what obsidian will actually survive.
| Method | Safe? | Why |
|---|---|---|
| Water | Yes | Safe in water. Quartz family stones are hard, non-porous and chemically stable, so a rinse does no harm. |
| Direct sunlight | Yes | Direct sunlight does no damage. |
| Salt or salt water | With care | Dry salt is tolerable, though it scratches a polish over time and there is no particular reason to use it. |
| Moonlight | Yes | Harmless to every stone on this list, which is most of why it is the method that suits everything. |
| Smoke, sound or breath | Yes | Nothing physical touches the stone, so nothing can be damaged by it. |
Worth knowing that obsidian is not a crystal in any technical sense: it has no crystal structure and it is geologically young, often only thousands of years old. Black glass is sometimes sold as obsidian, and since obsidian is itself glass, the distinction is about origin rather than material.
Two general rules that hold across the whole shop. If the price is far below everything else on the shelf of that size, something has been substituted or treated. And a stone sold with no locality at all is usually one the seller cannot trace, which in this trade often means tumbled, dyed and bagged somewhere a long way from where it came out of the ground.
Obsidian is usually linked to Scorpio and Capricorn, and to Pluto. Worth being straight about this: crystal and zodiac pairings are modern, they are not consistent between sources, and two reputable books will give you two different signs for the same stone. They are a useful organising idea rather than a tradition with a single lineage behind it.
If you want the part of this that does have a fixed method behind it, the Sun in Scorpio sets out what that sign actually describes, and it is calculated from a date rather than assigned by a writer.
Every piece of obsidian in the shop is the same stone with the same associations, which is both the appeal and the limit of it. A birth chart is the opposite: it is calculated from your date, time and place and it describes one person. If you do not know your birth time, this covers how to find it.
Yes. At Mohs 5 to 5.5 it is hard and chemically stable, so water does no harm.
No. Sunlight does not damage it.
Truth, grounding, cutting through. It is associated with the Root chakra.
Mohs 5 to 5.5. That is soft, so keep it away from keys, grit and harder stones.
Worth knowing that obsidian is not a crystal in any technical sense: it has no crystal structure and it is geologically young, often only thousands of years old.
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