the dead coral that washes up is what i was refering to, and yes, you can take it. I got that straight from the dlnr site.
http://www.hawaii.gov/dlnr/dar/libra...l_liverock.htm
The taking of sand, coral rubble or other marine deposits is permitted in certain circumstances. The material may not exceed one gallon per person per day, and may be taken only for personal, noncommercial purposes