If you're in a dilemma about whether you can wear your Green Kyanite Jewelry on a daily basis or not, it turns out that you can. The shimmering green crystal ranks 4.5 to 7 on the Mohs scale of mineral hardness, making it a durable, scratch-resistant stone that can withstand everyday wear and tear. However, it is a unique stone with two hardness depending on which side is being tested. It means it ranks 4.5 to 5 vertically while 6 to 7 horizontally, which made it once called "disthene," which means "two strengths."