Corundum Luster Explained: The Unique Shine of Ruby and Sapphire Crystals

Well, let me tell ya somethin’ about this here rock they call corundum. Now, it might not look all shiny at first, but don’t let that fool ya! This mineral’s got a kind of luster to it, ya know? They say it’s like glass, or sometimes like a pearl. Folks call that a vitreous or even adamantine luster, but really, it’s just got a bit of shine when ya look at it right.

Now, this corundum stuff, it’s tough, tougher than almost anythin’ else ya might pick up from the ground. They rate hardness on this fancy Mohs scale, and let me tell ya, corundum sits high on that thing! It’s a 9, only thing harder is a diamond, which is a 10. So ya could say corundum’s about as tough as they come. Heck, ya ain’t scratchin’ this stuff with just any ol’ tool, that’s for sure.

So what’s it look like? Well, if ya find some out in nature, it usually don’t look like much. Just rough pieces, kinda dull and maybe a bit dusty. Ain’t no gem yet! That rough corundum don’t look too special ‘til someone gets it all shined up and polished into somethin’ fancy, like a ruby or sapphire. Those are the real gems people pay top dollar for. But plain ol’ corundum, in the raw? Naw, that’s just corundum.

Now let’s talk about how heavy it feels. Corundum’s got a heft to it, ya see. It’s got a specific gravity – now, don’t worry about the fancy term – it just means it’s a dense one, heavier than ya might think for a stone that ain’t metallic. They say the specific gravity’s around 3.9 to 4.1. Compare that to other rocks, and ya feel the difference. Pick up a bit of corundum and ya know you’re holdin’ somethin’ solid!

This corundum’s also got a special way it’s built. It’s got hexagonal crystals—that’s a fancy way of sayin’ it’s shaped like a hexagon, or kinda like a stop sign, if ya think about it. Some pieces, they even taper down to a point, like a little pyramid on the end. But that’s just how it grows, all natural like. Some folks see these hexagonal shapes and think it’s just fascinatin’!

Another thing folks notice about corundum is how it breaks. Now, when most rocks crack, they just kinda split any ol’ way, right? But corundum’s got somethin’ called conchoidal fracture. That means it breaks in a sort of curved way, kinda like when ya break glass. Makes it extra strong and stable, though. Ain’t easy to chip this stuff, I’ll tell ya that.

Now, ya might wonder, what colors can corundum come in? All sorts! Comes in all colors, like a rainbow. But most of the time, if ya see it raw, it’s usually kinda plain and dull. Don’t start lookin’ like somethin’ special ‘til it’s cleaned up and maybe colored by bits of iron, titanium, vanadium, or even chromium—them’s the bits that can make corundum red or blue and turn it into a ruby or sapphire. But out in the wild? It’s often just cloudy and plain-lookin’.

And if you’re wonderin’ why folks make such a fuss over corundum, well, like I said, when ya polish it up, it can turn into a real treasure. A gemstone, they call it, when it’s cut nice and clean, especially if it’s sapphire or ruby. But remember, raw corundum ain’t the gem itself; it’s what folks do with it after that turns it into somethin’ worth wearin’ around the neck or on a ring.

So, there ya go, corundum’s a pretty interestin’ rock if ya think about it. Hard as can be, a little heavy, and shines a bit when ya look close. Don’t seem like much ‘til someone gives it the polish, but that’s what makes it special. Next time ya see a sparkly ring, could be corundum behind all that shine!

Tags：[corundum, corundum luster, gemstone, ruby, sapphire, mineral hardness, hexagonal crystal structure]