As I understand it.
Aragonite is a term that describes the material a substrate's primarily made of.
Aragonite is basically calcium carbonate or calcite, with other minerals present.
It can be sand or it can be mixture of larger particles.
Aragonite can even be pulverized to a very fine powder and comes in a liquid product to add to a tank.
Aragonite is sometimes used as a word to describe how the substrate appears - which is not always the case.
One of the lfs owners here in town uses mixed and crushed seashells as a substrate. Look like puka shells or mixed shell hash. He calls it aragonite - and it may very well be.
The best way to describe a substrate is to use the word that it's composed of, and the word that describes the appearance of it's particles, grain size and composition.
Such as
Aragonite fine oolite sand
Aragonite sand
Aragonite shell hash
Aragonite mixed shells
Silcon or quartz based sand
Crushed coral is sometimes made of calcite or calcium carbonate too. It looks like crushed up chunks or shells and coral skeletons.
The size and shape of the substrate is equally as important as the actual material it's made of.
Matter of fact - in a DSB - the mix of sizes and shapes of the sand grain particles may even be more important.
Here's some info that may help.
CaribSea
