Not all stones can become Alchemy Stones.
In fact, the vast majority of stones I see are not good candidates, at all.
Why, exactly, it stands out... I don't know. But I feel compelled to pick it up.
But that's only the beginning of the selection process.
The next step is purely kinesthetic.
Unless a stone "feels right" in my hand, it can't become an Alchemy Stone.
"Feeling right" is a pretty nebulous concept, as well, involving the surface texture of the stone, the shape, the size, its curves and more.
Then, of course, it also has to be visually appealing-- not just overall, but in such a way that a pattern will "fit" naturally with its shape.
The long and the short of it is that very few of the thousands of rocks I see during any given six-hour trip along the beach actually make it home. One some days I may return empty handed-- on others I may come home with as many as a dozen new stones.
Either way, a true Alchemy Stone is a rarity.