He shook his head. "Cut doesn't refer to shape, but the quality of the cut. Not all diamonds are cut kindly."

"You are enjoying this, aren't you?"

"I am."

"Doesn't the rock room have a computer exhibit on diamonds?"

"Yes, it does, but it's not nearly as interactive as I am."

Diane shook her head and laughed.

"I made you laugh. I'm making progress." Mike took a clear plastic container from the tray, removed a stone and held it in his hand. "Diamonds have a high refractive index. You want a cut that reflects the light out of the top of the stone and doesn't let light leak out the bottom."

"Leak out the bottom?"

"It has to do with the angle each facet is to the others. In an ideal cut, the arrangement maximizes the light's ability to disperse throughout the stone and reflect back out the top. A good-quality diamond can be ruined by a bad cut. When you said the diamond looked like a really good diamond, you were probably referring to how it glittered."

Diane thought a moment and met his gaze. "You're right. It sparkled."

"How large was it?"

Diane looked at her hand, visualizing Kacie's ring. She was fairly good at estimating measurements, hav ing measured so many skeletons.

"About seven or eight millimeters in diameter."

"That's about a carat. That is a respectable dia mond." He lay the stone in his hand out on a piece of cotton batting he took from the drawer.

"This is a carat diamond."

"It was about that same size. Do you have some thing black you could put it on?"

Mike shook his head. "You don't want to view dia monds against a black background. Black makes all diamonds look white, and you'll miss the light yellow tinge of a lesser diamond."

"I'm getting all kinds of useful information."

"That's what the museum's here for."

Diane caught a twinkle in his light brown eyes. "You're right about that," she said, smiling in spite of herself. Diane picked up the diamond and put it against her skin. "That's about the size of the one I saw. How much is this diamond worth?"

"This is a particularly good diamond. It's one carat-carat refers to weight, by the way. It's actually weight that matters and not size. This one is pretty much clear of flaws. It has what's called an ideal cut and is rated a D on the color scale, which is at the top of the colorless range. On the market, this would cost around ten thousand dollars."

Chapter 26.

Diane looked up at him sharply. "Ten thousand dollars?"

"Good diamonds are expensive."

"I didn't realize that diamonds are that rare."

"They're not. But over three-quarters of the world's diamonds are controlled by one company, and they're very good at making diamonds seem rare."

Diane picked up the diamond and studied it in the palm of her hand. "That's a lot of money for a diamond."

"You don't think your guy could afford that?"

"I haven't seen his bank account, but I would have thought it unlikely."

"Then it may not have been a diamond. We've been working on the a.s.sumption that the stone was a dia mond, but it takes an expert to identify one."

Mike reached in and pulled out several more plastic containers and lined up five stones on the batting. He dropped one of the lids on the floor and it started rolling. Diane reached down and picked it up before it got across the floor.

"I could have sworn you did that on purpose," said Diane when she rose and placed it back on the table.

"I did. I rearranged the stones. I thought I'd let you pick out the diamond."

Diane looked at the row of stones. They were all beautiful, all about the same size, and very similar.

"What if these get mixed up? Can you tell them apart?"

"Sure. I know in what order I placed them, and I have photos of their internal structures. Besides, I've got this sweet little device that'll identify them for me if I get mixed-up."

"That's good to know." Diane went down the row of stones, picking each one up, twisting it from side to side with her fingers, looking at the sparkle. She pushed one back. "I don't think it's this one."

"Very good. That's a white sapphire. The value is, I think, around a hundred thirty dollars."

She examined the remaining four again and moved another back and looked at Mike, who watched her closely with an amused glint to his eyes. "Cubic zirco nia. Maybe fifteen dollars," he said.

Diane moved another stone away from the line.

"Very good," said Mike. "That's a synthetic diamond-retails for about three thousand dollars."

"A lucky guess. They all look so much alike. But it had a slightly yellow cast to it. You're right. You'd have to look at it against a white background to see it."

Two were left. Diane picked them up and looked at them side by side. She moved them under the light. Weighed each in her hand, though she didn't know why. She had not a clue what it would mean if one were heavier than the other. It was the spar kle, she realized, she had used to eliminate the oth ers. She took another look at the stones, twisting them under the light. She set them down and moved a stone back in line with the others she had elimi nated, and looked at Mike. His eyes still cast that amused sparkle.

"Well?" she asked.

"You just eliminated the diamond."

"And I was almost sure."

"Nope. You were looking at the fire, weren't you?"

"Yes."

"This." He picked up the one remaining stone. "This is a moissanite-costs about three hundred dol lars. It has a higher refractive index than a diamond and is almost as hard."

"I've never heard of a moissanite."

"Silicon carbide crystals. It's named after Henri Moissan, a scientist from Paris. In 1893 he discovered the crystals in a meteorite. Naturally occurring mois sanite is rare, but a way to manufacture it was devel oped in 1995."

"Her diamond might have been any one of these."

"You have to look at the diamond's internal struc ture. Think she'll let you borrow it?"

"About as much chance as a s...o...b..ll's in h.e.l.l, I imagine. Although, if she thought it could help catch Chris Edwards' killer, maybe."

"Today, a lot of good diamonds are engraved on the girdle-on one of these tiny facets around the girth of the stone-with a serial number and a logo for where it came from. They are also fingerprinted-in a man ner of speaking. The internal structure of each dia mond is unique. People who deal in real diamonds are very concerned about distinguishing their product from the man-made variety."

"Tell me, if these nondiamonds are so much cheaper and you have to have a special machine to tell them from the real thing..."

"Why do people pay so much for diamonds? They are the stones created a billion years ago in the bowels of the earth-the mantle, actually-and were spewed out of the earth by a volcano in molten lava. It's the mystique, and very clever marketing by the diamond companies."

He picked up the diamond. "Besides, diamonds are cool stones. If the temperature and pressure had been a little less when it was being formed, we'd be writing with this in a pencil."

"I do know that graphite is carbon, and that dia monds are formed out of carbon."

"Did you know when light pa.s.ses through a dia mond, it slows down to half its speed?"

"I would have been more impressed if it speeded up," said Diane.

"You're a science fiction fan, aren't you? So am I. Another thing we have in common." Mike began putting the stones back in their marked containers. Instead of putting them back in the drawer, he set them aside in a tray. "Since they've been out of their boxes, I'll check all of them to make sure I didn't mix them up." He took them back to the storage room.

"I didn't know we have such valuable gemstones," said Diane, when he returned.

"Kendel's been helping to increase our number of reference gems. I tell you, if I'm ever on a scavenger hunt where my life depends on the outcome, I want that woman on my team."

Diane nodded and smiled. "I've been very pleased with her. Did she acquire the diamond we just looked at?"

Mike nodded. "She got it out of Mrs. Van Ross. We decided to keep it in the reference collection rather than exchange it with the one on display in the rock room. The one on display is a larger diamond but not near the quality, but with the lighting it's a little more impressive because of its size."

"It's on a black background, isn't it?"

Mike grinned. "Yep."

"Mike, I appreciate the lesson in diamonds." She stood up to go.

"Have you eaten?"

"Mike..."

"Come on, Doc. You have to eat. We could eat in the museum restaurant. We'd just have to walk downstairs."

Diane thought for a second. "Oh, all right. I am hungry."

"Great! Besides, I have something I need to ask you."

Between the sets of huge double doors at the en trance to each wing of the museum, Diane had added a new door that led down a long hallway to the restau rant that remained open after the museum closed. She and Mike took one of the elevators across from the rock room down to the first floor. It let them out at the midpoint of the hallway.

Photographs of pieces from the museum hung along the long walls-the inside spiral from a chambered nautilus, starfish, sea horses, seash.e.l.ls, rocks, minerals and gemstones, dinosaurs, wolves, b.u.t.terflies, birds and flowers. A preview of what the museum offered. Diane had framed several copies for her apartment. There was nothing as peaceful and soothing to her as a seash.e.l.l.

Several couples were walking down the hallway to the restaurant when Diane and Mike emerged from the elevator.

"Oh, the museum is still open. Let's go look at the jewels." A dark-haired woman in a black spaghettistrap silk dress decorated with stylized white b.u.t.ter flies punched the UP b.u.t.ton several times. "It's out of order." The man she was with and another couple stopped and waited.

"The museum isn't open," said Diane. "This bank of elevators is locked down for the night."

The woman looked Diane up and down. "How did you ride it?"

"I have a key."

"How do you get a key?"

"By being the director, Evelyn. This is Diane Fallon," said the man. From the wedding rings on their fingers, Diane guessed they were husband and wife.

He shook Diane's hand and introduced himself, his wife and friends. "You spoke at my club for lunch last month."

"Good to see you again," Diane began, but was cut off by the wife.

"So, you run the museum. What about this crime lab attached to it? That is just so strange. Should you be doing that?"

"Evelyn." Her husband sighed and smiled. The other couple examined the granite floor around their feet.

"Well, I want to know," she said, still looking at Diane for an answer.

"Rosewood had a need, and I was happy to be able to help," said Diane.

"I'm sure, but to think of autopsies being performed at the museum while people are looking at the exhib its. That's not going on now, is it?"

"We don't do autopsies. They are performed at the hospital. We examine trace evidence-fibers, finger prints, that kind of thing."

"I know I heard someone say that you examined bodies here."

"Perhaps they meant skeletons. I'm curator of the primate skeletal collection and I'm also a forensic an thropologist. I do look at bones here."

"Bones. I see. Well, we are so glad to have a restau rant of this caliber here, but I have to say-"

"Evelyn."

Evelyn ignored her husband, which, Diane imag ined, was something he was accustomed to.

"I can't say I like those computers there."