What is the defining trait of all minerals?

The Heart of a Mineral: It’s All About That Atomic Order

Minerals. They’re the silent, sparkling foundation of our world. From the mundane gravel under your feet to the dazzling gems in a crown, they’re everywhere. But what really makes a mineral a mineral? What’s that one thing that separates a chunk of quartz from, say, a piece of volcanic glass? Sure, there are a few rules a substance needs to follow to be considered a mineral, but the real key? It’s all about how its atoms are arranged. Think of it as the mineral’s secret recipe, its internal blueprint: a highly ordered atomic arrangement, also known as its crystalline structure.

Now, you might be thinking, “Okay, but what about all those other mineral-y things?” And you’d be right to ask! The International Mineralogical Association (basically, the mineral world’s governing body) has a checklist. To officially be a mineral, a substance generally needs to:

• Be born naturally, not cooked up in a lab.
• Be solid as a rock (literally!).
• Have a chemical recipe that’s pretty consistent, give or take a pinch of this or that.
• Be inorganic – no squishy, living stuff allowed (though, like everything, there are exceptions!).

But here’s the thing: plenty of materials tick some, or even most, of those boxes without actually being minerals. Take obsidian, for example. That shiny, black volcanic glass? It’s natural, solid, inorganic, and has a fairly consistent chemical makeup. But peek inside at the atomic level, and it’s a jumbled mess. No organized structure, no repeating pattern. That’s why it’s a “mineraloid,” not a true mineral. Close, but no cigar!

That ordered atomic arrangement? That’s the game changer. It’s what gives minerals their distinctive crystal shapes, that satisfying way they break, and even how hard they are. It’s like the difference between a perfectly stacked brick wall and a pile of loose bricks. Same bricks, totally different structure, totally different result. This internal order dictates the macroscopic properties that we observe.

Let’s take carbon, for instance. This single element can create both diamonds and graphite (that soft stuff in pencils). Both are pure carbon, but they couldn’t be more different! Diamond, the epitome of hardness and sparkle, versus graphite, soft and slippery. What gives? It’s all down to how those carbon atoms are linked up. In diamond, each carbon atom is locked tightly to four others in a super-strong, three-dimensional cage. Graphite? Carbon atoms form sheets, kind of like chicken wire, that slide past each other easily. Same ingredient, wildly different atomic architecture, wildly different results!

And speaking of breaking, that crystalline structure is also why some minerals exhibit cleavage. You know, that clean, predictable way some minerals split? It’s all about those planes of weakness in the crystal lattice, where the atomic bonds are a little less sturdy. Think of it like those perforated lines on a sheet of stamps – it’s just easier to tear along those lines. The quality of cleavage is described as “perfect”, “good”, “distinct”, or “poor”.

As of May 2025, the International Mineralogical Association recognizes a whopping 6,145 different mineral species! Each one has its own unique chemical recipe and, crucially, its own unique crystalline structure. And get this: if a chemical compound can naturally form with different crystal structures, each structure is considered a completely different mineral. Quartz and stishovite, both silicon dioxide, are a perfect example.

So, next time you’re admiring a sparkling crystal or just picking up a random rock, remember: there’s a whole world of atomic order hidden inside. It’s that internal structure, that crystalline arrangement, that truly defines what a mineral is. It’s not just about what it’s made of, but how it’s made. And that, my friends, is the heart of a mineral.