There are no such thing as astrological stones in the Sanskrit system of astrology. It is a popular myth that gemstones directly relate to certain planets.
It is said in Garuḍa Purāṇa that various stones and crystals have various effects – but these are not correlated to astrology. It is said in Bṛhat Parāśara and elsewhere that every planet represents a specific kind of gem – but these statements are right along side the different kinds of trees, humans, animals, seasons, and so on that each planet represents. The correlation here is for interpretation not for “upaye” (remedial measure / therapy). The Bṛhat Parāśara Hora has an extensive chapter on upaye, and Gemstones are conspicuous by their ABSENCE. The most important aspect of upaye – according to that respected Sanskrit text – is mantra, and personal pūjā (ritual worship of planetary deities).
I don’t know where the idea of “astrological gems” came from. Perhaps a scholar of western astrological texts could find a direct reference in Tetrabiblios or a similar respected text – and this would prove that it is not an idea native to Indian astrology.