Crystal
Yellow quartz — mostly amethyst that has been through an oven, and none the worse for saying so.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Natural citrine is genuinely uncommon. The overwhelming majority of what is sold under the name is amethyst or smoky quartz heated to somewhere around 450°C, which drives the iron colour centres from violet to yellow-orange. The treatment is stable, permanent and entirely legitimate; the problem is only that it is often unmentioned. Untreated citrine tends to a pale, slightly smoky lemon, while the deep burnt-orange stones with white bases are heat-treated almost without exception. Knowing which you have is a matter of looking at the colour distribution, not of paying more.
Practice has attached citrine firmly to money — the merchant's stone, kept in a till or a wallet — and unusually the association is recent enough to trace. It hangs on the colour's likeness to gold and on twentieth-century prosperity writing, not on anything classical; the yellow stones of the older lapidaries are usually topaz or chrysolite, which are different minerals entirely.
None of which need spoil it. A yellow stone in a dark month does something for a room, and citrine is one of the few stones whose folklore is cheerful rather than protective.
Readings practitioners have offered, ordered by how many recognise them. Take what serves, leave the rest.
Carried forward
Common in contemporary practice
Kept in a till, a wallet or a cash box. The tradition is a twentieth-century one and the reasoning offered is frankly sympathetic magic — yellow stone, yellow metal — which practitioners are generally happy to admit while carrying on regardless.
Carried forward
Common in contemporary practice
Sometimes said not to need clearing, on the grounds that it does not hold what passes through it. This claim is made for very few stones and nobody agrees on where it started.
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.