The ion microprobe was the department’s million-pound pride and joy. It was set up in a gloomy lab crammed with humming electronic equipment. The heart of the probe was a chest-high complex of stainless steel tubing and chambers. Rock samples, coated in gold plate, were fed into a vacuum chamber and bombarded with fine beams of caesium or oxygen ions, focused by intense electromagnets. There was a little optical microscope you could use to watch the ion beam cutting its little crater into the surface of the sample, like a kid with a magnifying glass scorching his initials on the barn door. But the sample areas were just microns across, only a couple of atoms deep. The layers of atoms, sputtered off into a mass spectrometer, revealed the elemental composition of the sample, and such details as the temperature the crystal structures formed at.

It was an impressive piece of equipment — one of just four in geology labs around the world — or at least it seemed so until you realized that Motorola alone had four of the beasts, for use in their silicon chip quality control procedures. The academic community was undoubtedly the poor relation of business and government, and in Britain things seemed to be even worse than in the States.

Henry’s work, it seemed, was next in the queue behind a meteorite analysis that was overrunning, after an all-night run. He argued, but got nowhere, and left fuming.

Anyhow, he suspected the composition of the samples wasn’t nearly so important, in this case, as their structure. And that was going to be difficult to study here, without the right tools.

When he got to the clean room Mike was there, bright-eyed and depressingly keen, eager to go over the results of X-ray diffraction analyses he had run on samples taken from 86047. The results were simple traces, peaks and troughs. Mike had run the images through the computer already, and was compiling the results when Henry arrived.

But Mike looked flustered, and he was rushing to be ready; Henry had a sinking feeling he had been up all night with this.

At Henry’s request, he had also run through some of the bizarre grains Henry had scooped up from the Arthur’s Seat dust pool, or whatever the hell it was.

X-ray diffraction was a step beyond the use of polarized light. The wavelength of visible light was much bigger than atomic size. X-rays had a wavelength just about the size of a typical atom, so they could show atomic structure: the crystal structure of silicates, for instance. The spacing of the peaks and troughs on Mike’s results showed the crystallographic spacing of the sample. The trick was to map back from these simple patterns to figure what the underlying crystal structure must be.

It was complex. But diffraction results were unambiguous. And every so often you would run into a new crystal form.