Crystal
Dark green chalcedony spotted with red — heliotrope to the Greeks, and the subject of one of Pliny's better sneers.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Bloodstone is a dark green chalcedony, coloured by chlorite or amphibole inclusions, spattered with red flecks of iron oxide. The other name, heliotrope, comes from a classical belief about how it behaves in water: dropped into a basin and held to the sun, it was said to turn the reflected light blood-red. It does not, though a dark green stone under water does peculiar things to a sunbeam and it is not hard to see how someone got there honestly.
Its most durable association is medieval and Christian — the red spots read as blood fallen on the ground at the Crucifixion, which gave the stone a place in devotional carving out of proportion to its material value. Before that it belonged to the amulet trade, and it is one of the stones for which the ancient sources make the most extravagant and least plausible claims.
Modern practice keeps it for courage and endurance, which is a considerable softening of the older lore. It is worth being straightforward: the historic association with blood is a matter of appearance and of record, not of demonstrated effect, and Duskveil makes no claim of any kind about what the stone does to a body.
Readings practitioners have offered, ordered by how many recognise them. Take what serves, leave the rest.
Carried forward
Pliny the Elder, Natural History, Book 37 (c. 77 CE)
Pliny reports that the magi claimed heliotrope, combined with a herb of the same name and the right words spoken over it, would render its bearer invisible. He calls this a most impudent lie, and the sentence is a useful reminder that scepticism about stone claims is as old as the claims themselves.
Carried forward
Common in contemporary practice
Carried before something that has to be got through rather than enjoyed. Practitioners describe it as a stone for endurance, and the shift away from the older blood associations towards plain stubbornness has happened almost entirely within the last century.
Credit what you carry. Much of this comes from living traditions, and some of it from traditions that are closed — held by particular peoples and not offered for general use. Where you know whose practice a reading came from, name them; where you don't, say that too.