Beads can be made from a wide range of materials, from glass to plastic to shell to painted macaroni. Here’s a list of materials of beads we find in the archaeological record:
Glass – Glass is the main type of bead we find, partly because once people knew how to make glass, they could make far more beads far easier from glass than they could from amethyst or shell or other materials. Glass also generally has a wider variety of colours and doesn’t break very easily when in bead form. If an object has air bubbles, it is most likely glass. Glass also tends to be fairly dense and therefore heavier, but there are certain stones and metals that are heavier than glass. You can also look for signs that the material was once plastic – tendrils coming off of the object or the sense that it is a liquid frozen in solid form.
Stone – This can be gemstones (e.g. amethyst, carnelian, agate, jade, etc) or other stones (e.g. soapstone or sandstone). Gemstones are far more frequently used to manufacture beads, due to their aesthetic quality and value. In the archaeological record, the stone beads we most commonly deal with are made from agate, carnelian, amethyst, garnet, or rock crystal. Stone beads are often marbled in colour and tend to be heavier than many other materials. They are also often more chipped than glass tends to be, due to the nature in which they are made.
Metal - Metals, particularly precious metals (e.g. gold and silver) are fairly common materials for beads (see the photo above for some gold beads). We also see metals combined with other materials to make beads, something we don’t usually see with other materials. Metal foil glass beads or stone or glass beads capped with metal are good examples of this. Metals are usually shiny, cool to the touch, good conductors of heat, and sometimes magnetic. Metals are often corroded in the archaeological record, so the shiny factor is often unhelpful, but corroded metals are often rusty orange or green in colour.
Amber – Amber is fossilised tree resin (not sap) from several now extinct species of pine tree. Its distribution is limited, and so its use in the ancient world is not nearly as prevalent as stone or glass. I have seen amber used most prevalently in European contexts, where sizeable deposits can be found. Amber is often a distinctive mottled orange/red/yellow colour, and shining a light through it shows a crackling effect.
Jet - There are two forms of jet, one formed through high pressure decomposition of wood in salt water (hard jet) and the other through high pressure decomposition of wood in fresh water (soft jet). Jet was used in jewellery primarily from the Neolithic through the end of the Roman period, but spans all periods in the archaeological record. To distinguish between jet and opaque black glass, hold the object in your hand. Jet is very light (since it’s less dense than glass) and not cool to the touch. Black glass is heavier (denser) and cool to the touch.
Bone – Certain beads are made from bone, usually from animals. I am including teeth and ivory in there, since the material is similar. Bone is usually white or a very light colour and porous or spongy. Bone is also incredibly light in weight. Archaeologists also often test materials using their tongue – the spongy nature of bone causes it to stick, whereas stone and other materials won’t. Note: Archaeologists merely touch the object to their tongue, usually when they can’t tell the material by sight. We don’t go around licking everything!
Shell - Shell has been used for beads for many millennia. They can be used whole or cut into shapes, and both styles have holes either drilled or rubbed into them. Shell is soft enough that rubbing on a stone will eventually create a hole. Drilling will probably work faster, but runs a much higher risk of breaking the shell. Whole shells should be easy enough to identify, while cut shells can be distinguished by the thin, hard, and often shiny nature of the material along with its light weight.
Ceramic - Ceramic beads are common, and many of us have made beads out of clay as children. You can usually see the original earthy nature of the material, and ceramics also stick to your tongue if you want to be sure. Ceramics are usually heavier than bone or shell, but lighter than stone or glass.