Until a few years ago, it was still considered the Holy Grail, technologically speaking, to be able to make gemstone-quality diamonds in a laboratory. Scientists have been trying to do it since the 1950s, with only limited success: The results were small (under a carat) and industrial-grade—great for use in cutting tools, given the hardness of diamonds, but not high-quality enough for engagement rings.

The machines and processes used to make man-made diamonds have become more refined in recent years, finally able to simulate the extreme pressure and temperatures deep within the Earth’s core that created organic diamonds over billions of years. Today’s lab-grown diamonds are finally of sufficient quality to be certified by third-party institutions, such as the Gemological Institute of America, as real. They have the exact chemical composition and structure—carbon atoms arranged in a cubic crystal formation—as mined diamonds.

A few companies have sprung up to sell gem-quality diamonds to the public—mostly as loose stones. But finding reliable sources and then having them set is arduous and ultimately a turn-off to consumers.

Enter Ada Diamonds, a new Silicon Valley-based company that is revolutionizing the business. The company works with individual clients to design unique pieces of jewelry. Customers can name the exact specifications they desire in terms of cut, color, clarity and carat weight (up to five carats). Ada’s founders, the husband-and-wife team of Jason Payne and Lindsay Reinsmith, say that Ada white diamonds have fewer impurities and defects than Earth-extracted stones, and are in fact 99.999% pure carbon, making them brighter, whiter, and stronger than most mined diamonds. The company can also make a rainbow of diamonds of the same quality.

The man-made diamond process allows for unusual new capabilities. Through the company’s signature Lavoisier process, you can supply Ada with “donor” material—most physical items contain carbon, the necessary ingredient—to create a truly bespoke stone. Ada sends you a small graphite container called a crucible, which you fill with whatever you like; customers have selected flowers, photos, fabric, wood, corks, documents—even locks of hair, baby teeth and ashes. The crucible is then sent through a process that “cooks” the contents down to pure carbon, which is then placed in a high-temperature, high-pressure diamond press. The whole procedure takes many weeks, and is nearly twice as expensive as a regular lab-grown diamond (which is in turn roughly 20% less expensive than a comparable mined diamond).

Jason Payne and Lindsay Reinsmith of Ada Diamonds.Janine Licare Photography http://www.janinelicarephotography.com

There are a few reasons for the higher cost of custom diamonds, according to Payne. There are additional fixed costs to process and purify the donor material into high-purity graphite. Also, the introduction of novel material into the growth cells increases the growth cycle failure rate, so more growth cycles are needed to ensure that a proper rough diamond is grown to satisfy the customer’s request. Lastly, the cutting of the rough diamonds to the customer’s specifications can result in the need to discard 75% or more of the weight of the rough diamond.

I met Payne and Reinsmith during this year’s Pebble Beach Concours d’Elegance weekend in Monterey, Calif. (Payne has a particular fondness for beautiful cars and speed.) The young couple hosted a pop-up boutique at the Rolls-Royce villa, an estate the luxury marque uses to host clients, dealers and media. Ada made custom jewelry specifically for Rolls—“RR” diamond cufflinks and tie pins for men, delicate diamond necklaces and earrings for women. I held a pair of striking blue diamond drop earrings worth $30,000 that someone had purchased earlier that day.

Since then, Ada diamonds were featured in another luxury automotive setting—the cockpit of a Koenigsegg Agera RS sports car named “Naraya.” Exactly 155 yellow Ada diamonds were inlaid in 18-karat gold to create a unique nameplate for the supercar, which won the top honor at this year’s Salon Privé Supercar Show held at Blenheim Palace.

“Every gearhead knows that synthetic oil, created in a laboratory, is far superior to ‘dinosaur oil,’” Payne told me. “It’s an easy leap for the enthusiast to comprehend that diamonds grown in a laboratory are objectively superior to ‘dirt diamonds’ as well.”

The world’s acceptance of lab-grown diamonds remains to be seen, but Ada’s founders point out several of the many benefits. “Lab-grown diamonds represent a true victory for the environment, human rights and diamond supply chain transparency,” says Payne. “Mining diamonds is an energy intensive and ecologically invasive procedure, affecting fragile ecosystems across the globe.” He points out that Ada’s customers feel reassured that their jewelry is coming from a known and socially responsible system, and that Ada is committed to giving a percentage of every sale to philanthropy to underline the company’s commitment to conflict-free diamonds.

There is also the benefit of sustainability. According to Bain & Company, 135 million carats of gem-quality diamonds were mined in 2015, up from 131 million in 2014. At that rate, demand for mined diamonds will outpace supply by 2019.

Is there a danger that lab-grown diamonds will flood the market and affect overall diamond values? According to Payne, this year approximately 100,000 carats of gemstone quality diamonds will be lab grown. To build production facilities large enough to generate one percent of the current mined supply would take hundreds of millions of dollars of capital expenditure and tens of millions of dollars a year just to run.

Says Payne: “It will take many years before lab diamond gemstones are anything more than a very small portion of the total diamond market.”