Crystal
Tree resin from a forest forty million years gone — warm to the touch, and the origin of the word electricity.
These are associations the community holds, not settled fact — the more a reading is shared, the bolder it sits.
Amber is not a stone. It is resin from conifers that grew around the Baltic in the Eocene, buried, polymerised and fossilised over some forty million years. It floats in salt water, which is why storms wash it onto the beaches of Poland, Lithuania and Kaliningrad and why it has been collected there since the Stone Age; the Amber Road carrying it south to the Mediterranean is one of the oldest trade routes in Europe. Because resin is sticky, some pieces contain insects, spiders, feathers and flowers, preserved in a detail no other fossil process approaches.
Rub amber on wool and it picks up hair and small pieces of paper. The Greek word for amber is ēlektron, and when William Gilbert came to name the force behind that effect in 1600 he coined electricus from it. The whole of electricity is named after this fossilised tree sap, which is not a fact many stones can offer.
A note on sourcing. Burmese amber, or burmite, is scientifically remarkable and comes out of a conflict zone in Kachin State; the trade has been linked to armed groups and to serious harm, and many researchers now decline to work on newly exported material. Baltic and Dominican amber carry no comparable problem. Practice keeps amber for warmth and for what has been carried a long way, and if a stone ever earned that reading by ordinary means, it is this one.
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 states flatly that amber is the resin of a pine-like tree, hardened by time and washed out by the sea, and demonstrates it by the insects found inside and by the pine smell it gives off when burned. He then works through the myths — the sisters of Phaethon weeping it, birds' tears, the urine of the lynx — and dismisses each in turn.
Carried forward
Common in contemporary practice
Worn against the skin, where it warms quickly and does not feel like stone. Practitioners describe that warmth as most of what distinguishes it, and it has an ordinary explanation: amber is a poor conductor of heat, so it takes body temperature and keeps it.
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.