Early last month when I was on my weekend hike, I accidentally dropped my iPhone face down on the cement.

As you might expect, the screen broke and made it unusable. Thankfully, I was able to get a Genius Bar appointment at the Apple Store that same afternoon and got the screen replaced for the hefty price of $150.

So in a column I did recently about what I wanted in a new iPhone, I lamented about my iPhone breaking and said I wanted a sapphire screen on any new iPhone I might buy in the future. I formed that opinion because of all the hype surrounding Apple buying $578 million worth of sapphire in way of partnership with GT Advanced, a sapphire manufacturing company. All of us assumed that this meant Apple would put sapphire screens in the new iPhones, but when it didn’t happen, I started digging into why this was not the case.

Many have suggested that the decision not to use sapphire was the result of manufacturing issues – that with more time, Apple would have used sapphire screens for the iPhone 6. As I looked closer at the Apple announcement, and after looking more at the benefits and drawbacks of sapphire, it seems that Apple had good reasons to go with ion-strengthened curved glass (Gorilla Glass) instead of sapphire.

While sapphire has been hyped as an alternative screen cover for smartphones, the continued use of strengthened glass has less to do with production issues and more to do with what smartphone manufacturers know about consumers, their preferences and, more importantly, how people actually use phones and what they’re willing to pay for them.

By the way, some reports stated that up until a few weeks before the iPhone announcement, Apple was going to use sapphire but dropped it because of yield issues. This is not true. My sources tell me that sapphire was never targeted for the iPhone 6 or 6 Plus and its role in future iPhones hasn’t even been decided yet. Also, anyone who knows the manufacturing process knows that to make tens of millions of screens for an iPhone launch, the orders for those screens had to be put in place well over six months ago and planned meticulously into the final manufacturing of these new smartphones.

Here is what I was able to find out about sapphire versus glass by doing many interviews and looking at the current research:

Design

The trend in smartphone design is to achieve thinner, lighter devices, while making them bigger at the same time. That’s not easy to do. To increase the size of a smartphone and still keep the weight down requires thinner, lighter material. What we know about sapphire is that it is more than 30% denser than glass and would require a compromise on both fronts for widespread use in phones. Corning has shown that it can manufacture Gorilla Glass to be thinner than a sheet of paper and strengthened with a process that makes it more damage resistant. Design flexibility and adaptability are important. The latest smartphone designs from Samsung, Apple and others include sleek displays with glass that curves to the edges of the devices. Because glass can be manufactured to extremely thin dimensions and still be chemically strengthened, it’s more flexible and can be formed and shaped into the sleek designs you see in the iPhone 6 and others. Sapphire is bulkier and must be cut into shape, creating both cost and production issues on larger surfaces.

Cost

Cost is a big factor with consumers, and the smartphone category is hugely competitive these days. Apple is already pushing the high end on price as comparable devices are priced at or lower than the iPhone 6, and it would have had to charge even more for a sapphire-covered phone. The cost to produce a sheet of sapphire is estimated to be roughly 10 times that of strengthened glass. In fact, one source I talked to said that cost could be even higher. Our researched opinion early on was that if Apple did add a sapphire screen to the new iPhone, it would add at least $100 to the base cost. That could be a deal-breaker for mainstream iPhone customers.

Battery Life

By far, the number one phone-related complaint from consumers is battery life, so manufacturers look at every component that draws energy and work to minimize the impact of each. And one of the biggest drains on battery life is the brightness of the screen. According to Bernstein Research — which conducted research on the benefits of glass versus sapphire as a cover material — glass transmits light much better than sapphire. Therefore, to get the same level of brightness using a sapphire screen requires more energy. That problem can’t be fixed easily, as the basic properties of sapphire make it transmit less light than glass. This also impacts other things like glare. Glass can have an anti-reflective solution embedded into the material, reducing the effects of the sun when reading outdoors. To achieve anti-reflection with sapphire, it has to have a coating applied which, over time, will wear off. This issue alone may make it tough for Apple to ever use sapphire in future iPhones, since most people have their iPhones for at least two years.

Environmental Impact

Manufacturers know that consumers are starting to care a lot more about the impact that the products they buy are having on the environment. Sapphire requires 100 times more energy to produce than glass. The energy requirements alone make sapphire problematic as a viable material to use on a smartphone. None of the folks I talked to had any idea how they could solve this problem given the nature of the material itself.

Durability

This is by far the most promoted benefit of sapphire, and perhaps the most misunderstood. This is the area I got tripped up by assuming too much from Apple’s investment in GT Advanced. Sapphire is extremely hard, which is to say highly scratch resistant. That is why it is found on products such as luxury watches. It is largely untested on phone screens, though. In fact, sapphire is a crystal that is very hard, but inflexible and extremely brittle. Sapphire’s inherent structure makes it susceptible to flaws that can occur along the crystal plane. I was told by multiple sources that various field tests subjected sapphire to scratch and break tests against strengthened glass. It performs better on scratch resistance, but when you drop it, it is more likely than glass to break. Glass actually flexes and can absorb the shock of a drop more successfully than sapphire. Sapphire is prevalent on luxury watches and other products that don’t experience the same drop risk as smartphones.

Like many who jumped on the sapphire bandwagon without really understanding it, I had assumed that it was unbreakable. But in talking to various experts, they said that the way to look at this is to think of a sheet of ice (also a crystal); small cracks weaken the surface and it will hold together for only so long before some impact will cause it to break. Those small cracks add up like the normal wear and tear we put our phones through every day – knocking around in our purses and pockets with keys and change, or scuffing against the surface of a counter repeatedly. Current solutions, such as Gorilla Glass, apparently are reinforced with a chemical that alters its atomic structure and actually strengthens the area around scratches to insulates the glass longer against breaking. While surface scratches may be more visible earlier on, a glass screen will stay more intact over time than a sapphire one. Once sapphire is exposed to a scratch or a flaw, visible or invisible, its risk of breakage and eventual failure is high. On watches, this is less of an issue because they are seldom dropped and the watch surface is smaller. But in a smartphone with a larger screen and many usage variables, it’s difficult to guarantee that it’s less prone to breakage.

I don’t doubt that over time, there could be some breakthroughs with sapphire and new coating processes that could make it possible to use on a smartphone. However, from the research I did, it does not appear that it could happen anytime soon. Plus, sapphire’s less flexible and more brittle nature suggests, as least to me, that using it in large-screen smartphones would still be difficult — even if it was possible to coat it in a way to keep the screen from splintering. I now at least understand why Apple didn’t use it in the new iPhones — and the more I study this, it seems that it could be problematic for Apple to use sapphire outside of its smartwatch line anytime in the near future.