Though he collects rocks, passively, Tyson doesn’t care as much for gems or precious metals.
His collecting is more sentimental than about the value of an item, and he tends to prefer simple jewellery over anything with gems anyway. In part that comes from his Synesthesia. There are already so many patterns and colours in his vision that it can become a little overwhelming to add more unnecessarily.
Even when he’s suppressing his Synesthesia, many of his decisions are shaped around that.
When it comes to metal, Tyson refers silver over gold. He doesn’t dislike gold, per say, but he is tired of seeing it as the ‘best version’ of everything. More generally, Tyson finds brass or copper to look more interesting than gold does overall.