There are a lot of myths and misinformation out there when it comes to diamond value, so let's try to set a few things straight.
Why a diamond, when cubic zirconia is so cheap?
While it's true that at first glance a well-cut cubic zirconia (for the record, a manmade zirconium dioxide as compared to the naturally formed nearly-pure carbon crystals that make up a diamond) may at first resemble a diamond, that will not last. Though all stones can pick up oil from our hands and in turn attract dust that dulls the sparkle, CZs actually absorb some of the oil, turning them permanently cloudy over time. Diamonds can easily be cleaned to restore their sparkle, but within a year or two of daily wear a cubic zirconia will not look nice at all, even with regular cleaning.
But what about another stone?
Of course, a colorless stone may simply not be your preference. Or you may be attracted by the lower price tag of moissanite or other lab-created gems. But there are some practical considerations that make diamonds superior for daily wear, such as in engagement rings. They are absolutely the hardest mineral on the planet, for starters. Even ruby and sapphire only come in at a 9, and moissanite at 9.5 compared to diamond's 10 on the Mohs scale. And it's not a linear scale; diamond is actually 4x harder than corundum (that's the mineral that is called ruby or sapphire depending on its color). It can withstand intense heat and caustic chemicals, and can only be cut or chipped by other diamonds or very precisely angled hits.
When cut well, diamond also has one of the best visual performances of all gemstones. It has the highest luster of non-metallic minerals, "adamantine," and one of the highest refractive indexes. RI is a measure of dispersion, the way light is separated into its component colors when it passes through the stone. This property is also described as 'fire,' for the way it causes the stone to sparkle as it moves and catches the light. Its RI is 2.417, and while moissanite is higher at 2.65, moissanite is doubly refractive and diamond is singly refractive. Double refractivity breaks up the reflections of light through the stone, so diamond has slightly less fire but more brilliance than a comparably cut moissanite. Brilliance describes the reflection of white light through the stone as opposed to the component colors that make white light.
But aren't they worthless as soon as you walk out of the store?
While it's true that you can't immediately sell back a diamond for what you paid for it, stones of more significant size (around a half carat and above), especially with a diamond report from a reputable lab such as GIA, are almost certain to slowly appreciate in value. The diamond market does not fluctuate as much as metal markets, so you shouldn't buy a diamond planning to sell it in a year or two for more than you spent. However, diamond prices have gradually gone up over the past decades. Markups, on the other hand, have actually gone down, in large part thanks to competition with internet retailers. You may have heard or read that there is a 100-400% markup on diamonds. Though this certainly was true, and may still be so for smaller stones, retailers are no longer able to sell for such high profit margins and remain in business. But in any case, a diamond should be purchased with the sentimental and lasting value in mind more than the immediate dollar signs.
But isn't that 'Diamond is Forever' slogan just marketing fluff?
If a little care is taken with regular cleaning and check-ups with your jeweler, a diamond ring can indeed last a very long time. It can be an heirloom to be passed down. Especially if you invest in a nice center stone, even if your future child or grandchild does not care for the style of the ring, they can have it redesigned and set the old and still perfectly good diamond in a new mounting. Each new wearer can add to the memories attached to the stone. It's a lovely way to start a tradition that doesn't have to be tucked away in a drawer like a photo album but can be worn and enjoyed every day.
How will you make your diamond memorable?