Hi rightwriter! Perhaps a few true stories will give you the proper perspective on this.
1) When I was in Ohr Sameach, they warned us not to learn Kabbalah. They said it is silly to work on Nistar before you finish Nigle. (Nigle means all of Shas both Bavli and Yerushalmi along with all 4 chalakim of Shulchan Orech and understanding all of the main poskim = Shach, Taz, etc.) Of course, some individuals decided to ignore that Psak. The results were disaster. Some of them went to Breslov and got involved with the whole mess that occurred there.
What’s that got to do with gemstones? Good question. The reason why we avoid Kabbalah is because (as the song says), “When you believe in things you don’t understand, it’s superstition.” Superstition can easily become Avoda Zara.
The big problem with something that is similar to Avoda Zara (like Yoga) is that ORTHODOX Jews have not violated the prohibition of Avoda Zara for thousands of years. Therefore, we don’t have a clear definition of what is or is not Avoda Zara. For instance, is a Sun Salutation Avoda Zara? After all, the original meaning of the movement was part of a Hindu worship that involved saluting the god of the sun. I asked this question to multiple rabbis. They all told me they don’t know. There is no gemorra that discusses Sun salutes. Why not? Because when the gemarra was written ORTHODOX Jews would never do something like that. The Shayla never came up. Similarly with gemstones (or crystals). Are they being used to cast spells? Invoke Occult powers? Would they be considered witchcraft? Magic? Any of the above is punishable with death according to the Torah. We don’t know. If you ask a Mekubal, they will tell you that most likely all of these “good luck charms” are worthless. The only thing that usually results from them is that the person using them violates some very serious Torah prohibitions.
Therefore, we stick to halachah. Unless you can find an HALACHIC source for doing something or not doing something, you can safely ignore it.
2) In the course of my travels, I met a Ba’al Tshuva whose mother owned a gemstone store. He told me that it is all sales hype. I suggest you stop trying to understand it beyond that.
3) Here’s a story about how not knowing what you are doing when it comes to Nistar can have tragic consequences. This story is from Shmuel Auerbach (the son of Rav Shlomo Zalman Auerbach). He said that at one time there was an amulet (kameiah) in Yerushalayim. This Kamaiah was allowed to be carried in a Reshus Harabim on Shabbos because a psak halacha had been given that it was known to be effective in curing people. Apparently it had been written by the Taz. It was once given to a Sofer to help him with an illness. This sofer assumed that the Kamaiah had some type of shaimos of angels or of Hashem written in it. The rule with a Kamaiah is that once someone opens it and looks inside, it stops working. He felt that this didn’t matter since he could just copy whatever shaimos were written there and make a new one. He opened it. It said, “in the zechus of the X times that I learned this Tosafos in Chulin which enabled me to get the correct psak, may the person who wears this Kameaih be healed.” Needless to say, the sofer could not duplicate that and the kamaiah stopped working. Think of all the people who could have been healed with that Kamaiah? One person decided that they were smarter than everyone else and ruined it. Similarly with gemstones, I would guess that there are lots of little details that can make things go very wrong.
For instance, wearing a ruby during pregnancy to prevent miscarriage. Great idea because it is mentioned in halacha. Or maybe if you don’t have this mesorah, it’s considered like New Age Avoda Zara? Highly unlikely you will find a Rabbi willing to pasken this shayla. Is it possible that a Sefardia whose mother wore a ruby while pregnant receives schar for doing a mitzvah while a BT who was influenced by New Age wearing a ruby receives the death penalty? Could it be that the same action results in a radical difference in the Din that depends on your Kavannah? A scary thought as we approach the Yom HaDin! Best advice is don’t mess around with the metaphysical side of Judaism if you don’t have the mesorah.
Tamim Tiyeh Im Hashem Elokecha!
Kesiva V’chasima Tova.