The lens search showed "Tianyan Stone." All the beads are about 8mm in size, and the diameter is about 4.5 cm. This is my first time listing items in this category, and I am not at all familiar with stones or gems, so the product name is the result of a Google Lens search. In the unlikely event that the product name differs from the actual stone name, the actual item takes precedence. Please be aware of this. I will list items whose names matched after multiple searches conducted in environments where the lighting changes in the morning, afternoon, and evening. These are quite old items. The elastic band can apparently be replaced, as seen online, so those who are interested may want to replace it. Please purchase only if you understand and agree with the above explanation. I cannot provide professional explanations like those of a specialist, so please understand.