If an enhancement filler has the same refractive index (R.I.) as the host gem, the fracture being filled virtually disappears. Arthur Groom‘s Excel emerald enhancement, for example, has an R.I. of approximately 1.57—the same as emerald. So why did Groom create Excel 1.52?

Fernando Garzon, partner in Groom’s Clarity Enhancement Laboratory (CEL) in New York, explains that Excel 1.52 is easier for gem labs to identify than original Excel. “The Excel 1.52 gives you a greater comfort level with identification,” he says.

It’s no coincidence that Excel 1.52’s R.I. matches that of cedarwood oil, reportedly the enhancement preferred by most emerald wholesalers. Cedarwood oil is generally assumed to be natural and long lasting, but most of what the industry uses is manufactured, and, like all oils, it eventually dries out or leaks.

Although Groom guarantees that Excel and Excel 1.52 won’t dry out or leak, the products are a difficult sell to the trade or consumer, says Gabriel Acuña of Gems Col. Ltd., a Los Angeles emerald wholesaler. “You have to disclose that this is a polymer, or a filler,” Acuña says. “With cedarwood, it’s an oil. They don’t consider oil as being a ‘filler.’ “

Robert Linder, a gemstone wholesaler at Lindeau Gems in New York, has joined the Excel advocates but says Europeans and Asians are still hesitant about adopting new enhancements. Nevertheless, he believes the United States will take the lead in the trade’s eventual acceptance of Excel.