Reader Emily makes a great point: trace impurities may not have much impact on the way a salt tastes, but the size and shape of the salt crystals definitely do. Very true. And again, that’s not because the salt is any different chemically, but because crystals of varying sizes and shapes have different surface areas, and so dissolve at different rates.
Salt grains come in two basic shapes: granules and flakes. Granules are the shape we’re all used to, the little perfect cubes we all know as “table salt”. If you remember from other discussions on the subject of crystals (fat crystals, starch crystals, ice crystals), crystallization is what happens when molecules of the same type start stacking up upon one another. Given that molecules of sodium chloride are cubical, it’s easy to see why they might naturally want to stack up into cube shapes. In fact, given the right conditions, salt can grow into huge cubical crystals known as halite, which can be anything up to 4 or 5 inches across.
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