There are plenty of beaches here that are coral sand beaches. But I don't collect sand from them. I consider that to be not only rude, but I'd be degrading a beach. No-no's. So I collect from places where rough seas and winds have thrown coral sand onto paths, beach parking lots, and rocky coasts. I don't need a lot of sand. A bucketful lasts quite a while.
Again, I don't collect from beaches. But there are places along the coastline where chunks can often be found among the rocks. As I walk along picking up trash (yeah, I clean up the shoreline whenever I do my collecting), I also pick up the coral rock I find here and there.
This comes from my own driveway. The vehicles gradually breakdown the lava gravel used to surface the driveway, creating sand.
I collect this along a section of coastline called Honuapo. I use the ocean water there to make sea salt. And I reserve a gallon or two for the compost bins.
I know ranchers who let me collect old cattle and horse bones from their pastures.
I use wood to heat my house. I also have two friends who do the same. They save their wood ashes for me, and I much appreciate it.
I make my own in a special set up designed to make biochar. I use tree trimmings from my farm for this purpose. It's mostly ohia, but also guava, eucalyptus, christmasberry, Norfolk pine, ironwood, and any other tree that I trim.
I'm fortunate to have a bank of this along the dead river bed running across my farm.
Feathers & Fur/hair
This comes partially from my own animals and partially from friends' livestock. Friends bringing me a bag of feathers or fur can go home with a bag of veggies from the gardens.
I collect fallen fruit from many properties. Some from my own, but mostly from other people. I keep a list of people who are happy to have me remove the fallen fruits from their lawns. I usually leave behind a bag of veggies or eggs in exchange.