Normally made from faience, a fused combination of crushed quartz and other components, the melon beads are found in military contexts in many excavations including those at Corbridge and Vindolanda. Examples of these large melon beads can be seen in most museums associated with sites of Roman military occupation.
The beads may have been some sort of signifier of rank or status, perhaps in the parlance of Time Team, 'high status objects of ritual significance' or HSoRS. Or they could have been part of the military culture, the Roman equivalent of the dogtag. There are almost as many theories as there are beads, but it does seem that the turquoise faience beads are extremely common in military contexts and there is also a line of thought that they are part of horse trappings, although what a horse is doing in the military baths where many of these beads are found is something no one seems to want to address.
Generally measuring from 18-20mm in diameter and varying in length, with an inner hole diameter of around 5mm, these beads are sizeable and substantial. As each bead is individual, they don't all have exactly the same dimensions. The wide range of bead sizes and colours show how popular they were, and also how individual each bead was.
Made in opaque turquoise glass, they are an excellent representation of what the faience beads would have looked like when new. Variations in colour are due to the content of colouring agents in the glass. Beads in transparent cobalt blue were also common, as shown in the photograph.
The photograph shows the variations in diameter and height of beads.