Q: Can a rosary be worn as a piece of jewelry?
A: “Sacred objects, set aside for divine worship by dedication or blessing, are to be treated with reverence. They are not to be made over to secular or inappropriate use, even though they may belong to private persons” (CIC 1171).
Essentially, sacramentals such as rosaries must be treated with respect, particularly if they have been blessed. Reverence is the attitude of awe or respect that is most often given to sacred things. By its very definition, it is an interior disposition that usually cannot be determined by onlookers by appearances alone. A person may be wearing a rosary as a statement of faith, to keep it handy for praying throughout the day, or to avoid losing it. Those reasons would be indicative of reverence and would not interfere with the canon’s directive that sacramentals must be treated reverently.
Ordinarily speaking, then, if someone is spotted wearing a rosary, he should be charitably presumed to be wearing it for just reasons. Only if the rosary is being put to an objectively sordid use (e.g., a rock star is using it as a prop in a music video, obscenely contrasting the symbolic purity of the rosary with the immodest or immoral actions of the performers) can we be sure that the rosary is being treated irreverently (
source,
scroll to Q&A #3).