From the wuxing perspective, it depends on the individual.  For some it is very beneficial, for some it's neutral, for some it's harmful.  Depends on your auspicious/inauspicious phases of qi ("elements").     The metals I wear are silver and gold, which is a feng shui recommendation for those who benefit from wearing metals.   Precious and semiprecious stones are also in the phase of Metal in wuxing (with some variations depending on color and brightness -- Metal-with-Fire, Metal-with-Wood, etc.).  The exception is jade, which is considered balanced and represents all phases working in harmony, with emphasis on Water and Wood (Kidneys and its "child" Liver).  Jade that has some green in it is considered particularly nourishing (Wood), while white jade is healing to the bones and blood, and "warm jade" (only read about it, have never encountered it, it's exceptionally rare) facilitates magic.  Don't let me digress any further, jade is a large area of study in taoism and I only know a bit.   Before taoism and Chinese astrology, I used to test stuff kinesiologically to determine if it's harmful or beneficial or neutral.  The most reliable version of this method requires an assistant -- and is pretty reliable with some practice and getting the knack of it.  I even did a double blind placebo controlled study of this method at one point, with accuracy of about 85% (which is much higher than that for most mainstream lab tests).