Blue Labyrinth by Douglas Preston, Lincoln Child Read Free Book Online Page B

slowly to reveal a blue stone. Paden, relieved that it was a mere identification problem, took the stone and examined it. “Turquoise,” he said, turning it over. “Tumbled.” He took a loupe off the worktable, placed it in his eye, and looked more closely. “It appears to be natural stone, not stabilized and certainly not reconstituted, oiled, or waxed. A fine, gemmy specimen, of an unusual color and composition. Most unusual, in fact. I’d say it’s worth a fair amount of money, perhaps more than a thousand dollars.”
    “What makes it so valuable?”
    “Its color. Most turquoise is sky blue, often with a greenish cast. But this stone is an unusually deep, deep blue, almost in the ultravioletspectrum. That, along with its surrounding golden matrix, is very rare.”
    He removed the loupe, held the stone back out to the FBI agent. “I hope I’ve been of assistance.”
    “Indeed you have,” came the honeyed return, “but I was hoping you might tell me where it came from.”
    Paden took it back, examined it for a longer period of time. “Well, it’s certainly not Iranian. I’d guess it’s American—southwestern. Startling deep-azure color with a golden spiderweb matrix. I would say this most likely comes from Nevada, with Arizona or Colorado as outside possibilities.”
    “Dr. Paden, I was told you were one of the world’s foremost experts on turquoise. I can see already that I was not deceived.”
    Paden inclined his head. He was surprised to meet someone from law enforcement as insightful, and as gentlemanly, as this fellow.
    “But you see, Dr. Paden, I need to know the exact
mine
it came from.”
    As he spoke, the pale FBI agent looked at him most intensely. Paden smoothed his hand over his bald pate. “Well, Mr., ah, Pendergast, that’s a horse of a different color.”
    “How so?”
    “If I can’t recognize the source mine from an initial visual examination—and in this case I can’t—then testing of the specimen would be required. You see—” and here Paden drew himself up as he launched into his favorite subject—“turquoise is a hydrous phosphate of copper and aluminum, which forms by the percolation of water through a rock with many cavities and empty spaces, usually volcanic. The water carries dissolved copper sulfides and phosphorous, among other things, which precipitate in the interstices as turquoise. Southwestern turquoise almost invariably occurs where copper sulfide deposits are found among potassium feldspar bearing porphyritic intrusives. It can also contain limonite, pyrites, and other iron oxides.” He rose and, moving fast on stubby legs, walked to a massive cabinet, bent over, and pulled open a drawer. “Here you see asmall but exquisite collection of turquoise, all from prehistoric mines. We use it to help archaeologists identify the source of prehistoric turquoise artifacts. Come, take a look.”
    Paden waved the agent over, then took the turquoise sample from him and rapidly compared it with others in the drawer. “I don’t see anything close to a match here, but turquoise can vary in appearance even from one part of a mine to another. And this is only a small sampling. Take this piece of Cerrillos turquoise, for example, from the Cerrillos mines south of Santa Fe. This rare piece comes from the famed prehistoric site known as Mount Chalchihuitl. It’s ivory with a pale-lime matrix, of great historical value, even if it isn’t the finest quality. And here we have examples of prehistoric turquoise from Nevada—”
    “How terribly interesting,” Pendergast said smoothly, stemming the flow of words. “You mentioned testing. What sort of testing would be necessary?”
    Paden cleared his throat. It had been mentioned to him more than once that he had a tendency to run on. “What I’ll have to do is analyze your stone—turquoise and matrix—using various means. I’ll start with proton-induced X-ray emission analysis, in which the stone is bombarded with