@Moon Breaker: Thanks for your feedback! - I bumped it back to +1/+1 and increased the base value. I'm going to add a few more interactions with other symbols to make it more integrated, in a way similar to what I've just done with Coin Stack.
I'm going to update this later or next year - any suggestion is welcome :)

Since Geologist already destroys pearls for a permanent +1 per pearl, keeping the necklace at +0.5 per pearl would easily see it get outclassed.