You might be disappointed: Hawai‘i does not have a state mineral.
We know this is not what you hoped for, because we get this question a couple of times a year. Our Hawai‘i Islands are mainly lava, and therefore we don’t really have a state mineral.
The official State Gem listed since 1987 is ‘black coral’.
Black coral is the skeleton of a marine animal and not a mineral in the ‘traditional’ sense. It can only found on the ocean floor and to requires scuba diving and permits. Black coral is explored by some commercial enterprises, but not really something any of us from the Hawai‘i Rock and Mineral Society could ‘collect’. There are commercial enterprises that offer black coral from Hawai‘i for sale. If you are interested in owning some, please google it. Please make sure they certify it is really from Hawai‘i, and sustainably harvested, and be aware: you might get a sticker shock.