Did Apple invent a new gold for its luxury watch?

Gold investors have been positively giddy ever since Apple (AAPL) announced it planned to make a high-end watch with 18-karat gold casing. With Apple's sales might, the company could end up using as much as 30 percent of the world's annual gold production, some speculated.

It turns out that Apple probably won't upend the world's gold supplies. The company has been creating custom blends of gold to make its watches tougher and more resistant to scratches. But those recipes may not call for as much gold as people think.

Among the three Apple Watch collections Apple unveiled Monday, the priciest one, the high-end "Edition," costs between $10,000 and $17,000 and is made from custom alloys of rose or yellow 18-karat gold.

What exactly is in that custom alloy? That's a mystery Internet sleuths were trying to solve this week. Apple's team of metallurgists has been busy tinkering with gold blends, and even filed a patent application in December for a new type of blend that uses "as little gold as possible."

Generally, 18-karat gold is 75 percent gold by mass, with the remaining 25 percent made of nickel, copper, zinc or other metals. Pure gold is too soft for jewelry -- and certainly for a watch -- so the other metals help make 18-karat gold more durable.

Apple needed to find a way to make its 18-karat gold extremely tough. Its patent application describes an 18-karat metal matrix composite formed by blending gold and ceramic powders into a mixture that is compressed and then heated. The ceramic powders could take many forms, according to the patent, including diamond, garnet, sapphire powder, zirconia and tungsten carbide. The blend could change depending on the color or density desired.

But is the gold described in Apple's patent the same gold blend used in its pricey Edition watch? The company did not return a request for comment. But it did post a video on its website saying that the Edition watch alloys include silver, copper and palladium. Apple doesn't say if other ceramic materials are also used.

Apple's design guru, Jonathan Ive, explained in a Financial Times interview that the molecules in Apple gold are closer together, which creates more hardness than standard gold. That claim was met with some skepticism online. "Has Apple finally left a reality-based existence behind it?" asked Ars Technica.

Over at Slate, Jordan Weissman suggested that the technology could mean that in Apple watches, gold makes up 75 percent of the mass but just 28 percent of the volume. In other words, when Apple pours the gold blend into a mold to form the watch's shell, the non-gold ingredients take up most of the space.

"Apple gets to use less gold per cubic centimeter and still call it 18-karat," Weissman wrote. "It gets to stretch its gold out further than, say, Rolex would, to make a watch this size and shape."

Whatever's inside the gold, it's clear that for all its technological innovations, Apple still prizes a science that dates back thousands of years. "New Apple products give metallurgists street cred," gushed metals engineering group ASM International last fall.

  • Kim Peterson

    Kim Peterson is a financial journalist covering business and the economy. She has written for several online and print publications, including MSN Money and The Seattle Times.