This brooch was bought by a family member in New Zealand in the 1960s and is made of Paua shell and sterling silver. It looks nice on the collar of a black coat.
When I was in New Zealand 17 years ago I bought a pair of paua shell earrings set in silver, they were not cheap. I did not know if it was the poor exchange rate with the US Dollar, but most of the jewelry set in silver and paua shell was a bit pricey. It looked to me like abalone shell and when set in silver, somewhat inexpensive.