What is the ruling on men wearing a necklace if it is common among them and not for the purpose of imitating women, and is it actually considered imitating them?

The prohibition of men imitating women and women imitating men is firmly established from the Prophet, peace and blessings be upon him. This includes clothing, adornment, speech, gait, and everything that typically or naturally pertains to one of the two genders. If a certain garment is known in a country to be part of women's attire, then for men to wear it is considered a forbidden imitation. As for the necklace you mentioned, it is not permissible for you to wear it, because it is not known in Saudi Arabia to be part of men's attire, and only those who imitate women or the wicked wear it.