When I proposed to my now-wife, I didn’t have a ring. Finding the ring size of someone who doesn’t wear many rings seemed hard, getting and keeping one in secret seemed harder, and I didn’t see the point when really I just wanted to marry her. She said yes anyway. (I think she liked me.)
That made me her fiancé, but, in one of English’s few remaining vestiges of nouns with grammatical gender, it made her my fiancée. Most fiancés have fiancées with diamond rings, both because of some pretty impressive marketing and because diamonds are well suited for finger adornment. When cut right, diamond can exhibit total internal reflection, where (loosely speaking in a way that would make some people mad) an incoming ray of light bounces around multiple times inside the diamond before coming out. This property makes diamonds seem to glint and shine from all angles, which in turn makes them glimmer when they’re on something that moves around a lot—like a finger.
Some diamonds are synthetic and some form from asteroid impacts, but let’s ignore them so that I can say: Diamonds are forged deep within the planet, when buried carbon is squeezed by immense pressures from something like colliding (or newly forming!) tectonic plates. The incredible pressure shoves carbon atoms into their most rigid possible arrangement—so tightly and perfectly packed that it’s nearly impossible to move an atom out of the way. This makes diamonds incredibly hard to scratch. But it also makes them relatively rare, at least compared to normal rocks. So as cool as it would be to live in a diamond house, it’s just not happening.
Instead, we make homes out of much more common stuff. We use wood where there’s a lot of wood. We use stones, sand, and water (and other stuff) to make concrete. We use mud and clay to make bricks. We use sand again to make windows. All of them make for a pretty sturdy shelter. And, honestly, I’d rather have privacy than a diamond house, anyway.