Just as an aside. Tahitian moon sand is *black* for a very good reason, and it is some of the only truly black sand in the world because.....
There are two main types of rock in the world: 1) black oceanic crust created at mid-ocean ridges and hotspots by the moving of magma from the earth's mantle (below the crust) and 2) granitic white-to-gray-to-brown continental rock, which is older than the oceanic crust, silicon-rich, and has risen to the surface of the earth and above the oceans like scum on water because it is lighter than other iron-rich rocks (such as basalt).
Most sand is white to light brown because is is the result of continental erosional processes. Mountains of granite and other similar continental rocks are eroded. The rocks are broken into pebbles and eventually sand and silt, which accumulate at the points farthest from the mountains--beaches (usually).
Tahiti, like Hawaii, is very different from this... It is an island hotspot, not part of a continent, and not made from continental granites. Tahiti is a part of a volcano chain produced by magma (lava that hasn't erupted) that wells up from the mantle of the earth. The magma builds up and creates huge volcanos, and as the Pacific plate (tectonic plate) moves across this unmoving mantle hotspot, multiple volcanos are created in a row, creating an island chain (see Hawaii as the best example of this process).
When these volcanos become high enough to protrude from the water, they become islands, and exposed to the elements. The rain and wind erode the black basalt (the cooled magma) that make up the islands, and this basalt becomes a sand. So, unless you're on a mantle-plume hotspot, you won't find black sand!
Tahiti, Hawaii, and a few choice other hotspots are the only examples of dark black sand in the world because of this amazing geological process. That make sense?
I didn't need to explain that, but I thought some ppl might like to know why Tahitian Moon Sand and Hawaiian black sand are so unique. What a geology nerd I am........................
