For St. Augustine "The stars predispose, but do not determine", in short, they give inclinations that can be followed or not. For example, if the Stars push you towards introversion, as happens for example to those born under the sign of Capricorn, this does not mean that, if you wish, you cannot become a magnificent entertainer and the soul of the party! It will perhaps be more difficult for you, you may be less spontaneous at first and perhaps your style may be a bit unique, but that doesn't mean you can't become what you want most. We also consider that the environment in which we grow up and the experiences we have can greatly influence our disposition.
Very often in the creation of personalized malas I am asked for the stones associated with your sign and in this context the searches are lost everywhere, making it almost seem that almost every association seems suitable.
My curiosity about crystals comes from here: years ago, wanting a bracelet with the stone of my zodiac sign, I decided for a bracelet in black onyx, a stone that the web indicated to me as "the stone of Capricorn" and I began to carry it every day. This mistake cost me nightmares for weeks, at a time in my life when I still absolutely did not believe in the power of crystals. It was a lucky mistake that brought me here now.
In any case, there is no perfect association between stones and sign, which however should also take into account at least ascending and descending, but it is often a simple indication. Personally I was inspired by several books, from my knowledge and experience on crystals, from Archetypal Astrology and above all from Vedic Astrology which gives a lot of importance to the use of stones to balance and harmonize the most difficult aspects of the birth chart. In particular, I was also guided by a splendid work by Judy Hall on these associations which, I repeat, should in any case be considered only as suggestions.
To choose the right stones, it is necessary to always take into account the multiple facets of each personality, the moment that the person is going through, and finally, but obviously not least, the wishes of her and on which aspect you want to work more. Each person is a complex, unique and irreplaceable being and at every stage of his life he may need different stones and energies.