Crystal
A family, not a stone — and the deep red that lit the Anglo-Saxon hoards.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Garnet is a group of related silicates that share a crystal structure and swap metals about within it: almandine is the iron member, pyrope the magnesium one, spessartine manganese, grossular and andradite calcium. The result is a family that spans deep red, orange, green, and — in the rare colour-change varieties — both at once depending on the light. Everything sold as garnet is one of these, and a red garnet may be any of several species.
The Anglo-Saxon and Merovingian goldsmiths built their finest work on thin garnet plates set over hatched gold foil in cloisonné cells, so that light entering the stone bounced back through it; the shoulder-clasps from Sutton Hoo are the best-known example in Britain, and the garnets in them came, on current analysis, from as far as India and Sri Lanka. Bohemian pyrope drove a Central European industry for centuries.
Practice reads garnet as commitment and endurance rather than passion, despite the colour — the stone of finishing things, of staying. Where the old lapidaries treat red stones under Mars, the modern reading has drifted towards the steady rather than the martial, and the two now sit somewhat uneasily beside each other.
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 groups the red fiery stones as carbunculi — little coals — and sorts them by how they behave in the light rather than by anything we would call composition. His category almost certainly contains garnet, spinel and ruby together, and disentangling them from his descriptions is a lost cause.
Carried forward
Common in contemporary practice
Given at the end of something rather than the beginning — an anniversary stone in a way that has nothing to do with the modern birthstone lists. Practitioners describe it as being about staying rather than starting, which sits awkwardly with the fire correspondence and is rarely reconciled.
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.