Obsidian in Depth
Glass, not crystal
Obsidian is not a mineral at all. It is volcanic glass, formed when high-silica lava cooled so fast that atoms never had time to arrange into a crystal lattice. Chemically it is around seventy percent silica with alumina, iron, and magnesium, and the same composition that would produce granite if it cooled slowly. Because it is amorphous, it has no cleavage and no crystal faces.
What it does have is conchoidal fracture, breaking in smooth curved shells with edges that can be sharper than a surgical scalpel. Mesoamerican cultures built entire tool industries on this, and obsidian blades still get used in some specialized surgery. Varieties come from what got trapped inside: snowflake obsidian has white cristobalite spherulites, rainbow and sheen obsidian have aligned nanoparticle inclusions, mahogany obsidian has iron oxide banding, and Apache tears are small rounded nodules weathered out of perlite.
The safety point worth taking seriously
Broken obsidian is genuinely dangerous. A dropped sphere or a chipped point produces flakes that will cut skin without you noticing the moment it happened. Handle knapped pieces, arrowheads, and any raw shard with care, and clean up breakage with a damp paper towel rather than bare fingers so you catch the slivers.
It is also relatively soft at 5 to 5.5, so it scratches easily and polished mirrors scuff. Store it padded and separate. Water is fine chemically, but any piece with hairline fractures will fail under thermal shock, so skip hot water entirely.
How it is worked with
The tradition around obsidian is unusually blunt: it is described as a stone that shows you things rather than comforting you. Polished obsidian mirrors have a real history in scrying, most famously the one attributed to John Dee, now in the British Museum, which came from Mexico. Modern practice still uses obsidian mirrors and spheres for reflection work in dim light.
For daily use, a small tumble is carried as a grounding piece, and larger pieces get placed at doorways. Many practitioners advise against sleeping with obsidian nearby and against carrying it constantly during hard emotional periods, since the common report is that it brings things up rather than settling them. Treat that as a caution about intensity, not as therapy.
Pairings
Scorpio and Capricorn are the usual sign associations, and it works at the root chakra almost exclusively. Snowflake obsidian gets softened associations because of its gentler appearance, though mineralogically it is the same glass.
It goes with hematite for straightforward grounding and with black tourmaline when the concern is boundary rather than insight. Pairing it with rose quartz or amethyst is the standard advice when obsidian alone feels too stark, giving the arrangement somewhere soft to land.