Earlier this week, YouTube vlogger Marques Brownlee showed what appears to be a sapphire display for the next iPhone. While the use of sapphire won't be confirmed (or denied) by Apple until the product is released, the idea that it would want to use the material in its next flagship smartphone isn't too hard to believe: The company announced late last year that it partnered with leading sapphire producer GT Advanced Technologies to build a manufacturing facility in Arizona. And according to a report from 9to5mac, the deal included enough new equipment to make around 100 million to 200 million iPhone-sized displays per year.

There's one major reason why manufacturers are looking into using sapphire displays: The material is strong. Very strong. Sapphire is about four times as tough as glass. Gorilla Glass, regularly found protecting current smartphone screens, fares pretty well against hard objects too, but in order to scratch sapphire, you'd need to find something higher than nine on the Mohs scale -- a system of measurement used to rate mineral hardness from one to 10, with 10 being the highest. (For comparison, Gorilla Glass rates a seven; sandpaper is a nine; and diamond is a 10)

It's no coincidence that existing sapphire display phones are incredibly expensive.

Using sapphire instead of glass for a smartphone display isn't a groundbreaking concept. The material is already used in the (admittedly far smaller) protective glass covering the iPhone camera, as well as the 5s home button (for Touch ID); and luxury brands like Vertu, Savelli and TAG Heuer use sapphire displays in their existing phones. However, it's no coincidence that existing sapphire display phones are incredibly expensive -- manufacturing sapphire is time-intensive, limited by available quantity and very costly. The price of sapphire camera lens covers is 2.6 times higher than glass. On a large phone display, the difference in cost is even higher; last year, GT Advanced reps estimated the cost for a pane of Gorilla Glass at $3, while sapphire was around $30.

I reached out to multiple representatives from major smartphone players and while most companies I talked to had already researched and analyzed the possibility of using sapphire, their impressions were much more lukewarm than I expected. "The cost and supply aren't where we'd like them to be for sapphire to be practical just yet," said Ken Hong, Global Communications Director for LG. "Sapphire's durability and scratch-resistance are certainly attractive, but Gorilla Glass isn't going to be displaced anytime soon."

"Right now, the cost doesn't justify the nominal benefit of sapphire over Gorilla Glass"

There are plenty of other issues associated with sapphire. It's heavier than Gorilla Glass and the material remains less transparent than glass, meaning it would be more difficult to see the screen unless manufacturers add a special coating to increase transparency. (Even then, it still wouldn't be as good as glass.) Additionally, each representative I talked to confirmed that while sapphire is durable, it certainly isn't unbreakable. In fact, the larger the display is, the more brittle it becomes; "The sapphire is too hard to withstand bending," said a representative of a top-tier phone maker who also asked to remain anonymous. "It's easier to break during drop tests when the size of sapphire increases."

Another representative replied, "In a cost-benefit analysis, I doubt [using sapphire] makes sense, unless there is some perceived marketing advantage." Despite the potential downfalls of using such a material, that's exactly what Apple would be gunning for by using the display in the iPhone: marketing power. Sapphire's got a solid reputation; if the new iPhone features the same material used in premium watches, necklaces and earrings, and the company can throw it in without raising the price to consumers, Apple has a great new way to distinguish itself from the competition.

Only large companies with enough resources and bargaining power will be able to secure enough sapphire for mass production.

Even if other phone makers wanted to use sapphire displays, it would be difficult for them to secure enough inventory due to a very limited supply -- a problem that the iPhone maker has avoided. "Apple uses its massive cash hoard to fund big upfront commitments for key components," said Jan Dawson, chief analyst at Jackdaw Research. "[It's] something that almost every other OEM but Samsung will struggle to do." In other words, only large companies with enough resources and bargaining power will be able to secure enough sapphire for mass production.

This doesn't mean that sapphire displays won't be embraced in the future; they might just come in a different form. We wouldn't be too surprised if multiple hardware manufacturers decided to use the material on smartwatches for now, since the screens -- and the number of devices to build -- would be much smaller and thus more affordable than smartphones. (The Moto 360, for example, is rumored to have a sapphire screen.) Then, as supply goes up and production becomes more cost-efficient, more doors may open for phone makers who want to give sapphire a shot.