Amulet.
A small object, often worn, carried, or hung in a doorway, kept for its protective influence against harm or misfortune.
An amulet is an object kept for protection. The word descends through Latin amuletum, recorded by Pliny the Elder in the first century CE, with roots that may reach further back to Arabic himalat, "something carried." The function itself is older than any of these names. It is one of the oldest documented human behaviours: a small thing worn, carried, or placed at a threshold to ward off harm, illness, the evil eye, or whatever the local tradition feared most. Where a talisman is traditionally said to attract, an amulet is traditionally said to repel.
Historical practice
Examples are everywhere once you start looking. Ancient Egyptians wrapped scarabs, Eyes of Horus, and djed pillars into mummy linens, each chosen for a specific protective function. Mediterranean cultures from Greece to modern Turkey hang the blue nazar glass eye in homes, cars, and over cradles to deflect envy. The hamsa, an open palm sometimes set with an eye at its centre, appears across Jewish, Muslim, and North African households. Roman families hung bullae around the necks of freeborn children until they came of age. Norse rune stones, Anglo-Saxon herb bags, Celtic knot pendants, and the tiny carved gems set into Greco-Roman rings all served the same broad purpose. Many were minerals, often engraved with names, sigils, or short prayers, and either worn on the body or hung in doorways and over beds.
The medieval lapidaries (manuscripts cataloguing the supposed virtues of stones) treated this as serious knowledge. A jasper might guard against fevers, a sapphire against the evil eye, a coral against storms at sea. The line between medicine, religion, and protective magic was thin and often deliberately blurred.
Modern usage
In modern crystal practice the amulet idea survives quietly. A piece of black tourmaline by the front door, a small obsidian in the car, a hematite ring worn in crowded places, a smoky quartz tucked into a child's school bag during a hard term. Common stones reached for include black tourmaline, obsidian, hematite, smoky quartz, garnet, jet, and onyx, all chosen for their grounding or absorbing reputation.
It is worth being honest about what an amulet does and does not do. There is no measurable evidence that a stone in a pocket alters traffic patterns, neighbours' behaviour, or pathogens in the air. Buying a black tourmaline will not replace a smoke detector, a conversation with a difficult colleague, or basic safety habits. The wellness market sometimes blurs this line, marketing stones as substitutes for medical, legal, or practical action, which is where the tradition is misused.
The honest mechanism is closer to what the old practitioners likely understood already. An object that carries a clear protective intention reminds the carrier to stay alert, to set a boundary, to leave a situation that feels wrong. It marks a threshold of attention. Worn long enough, it becomes a small habit of self-protection made portable. That is not a trivial thing, and it is not a magical one. Related practices include talismans (the attracting counterpart), warding rituals, threshold blessings, and the carrying of saints' medals or scriptural verses, all of which work on the same human instinct: that a small object can carry a clear promise the wearer has made to themselves.