Tanzanite
On the label: Tanzanite · Gemstone
What it is
Blue-violet zoisite from one area of Tanzania; almost all is heated from brown. Mohs 6 to 7 and cleaves easily; a pendant stone more than a ring stone.
Gemstones: Natural gemstones, as mined and cut. Hardness (Mohs scale) says what scratches what; treatment (heat, oil, dye) must be disclosed under FTC rules.
Wikidata: Blue to purple variety of the mineral zoisite. Q429942 →
In the research
No PubMed papers mention this material with jewelry, allergy or eyewear; that is usual for findings and trade terms.
Other gemstones
Clasp & Lens describes materials from the public record and does not appraise, grade or test pieces; what a listing states is the supplier's statement. If a piece causes a rash, take it off; a reaction that spreads or blisters is a doctor's question, and sunglasses are no substitute for impact-rated eye protection where that is required.