The Mephisto Club

from the Greek word for blood. Because it’s sometimes red.”
    “Do they use the natural stuff in art supplies?”
    “We did find a few specialty chalks and pastel crayons that use natural hematite as a pigment. But chalks contain calcium carbonate. And manufactured pastel crayons usually use a natural glue to bind the pigment. Some kind of starch, like methyl cellulose or gum tragacanth. It’s all mixed together into a paste, which is then extruded through a mold to make crayons. We found no traces of gum tragacanth or any binding starch in the crime-scene samples. Nor did we find enough calcium carbonate to indicate that this came from colored chalk.”
    “Then we’re not dealing with something you’d find at an art supply store.”
    “Not locally.”
    “So where
did
this red stuff come from?”
    “Well, let’s talk about this red stuff first. What it is, exactly.”
    “You called it hematite.”
    “Right. Anhydrous iron oxide. But when it’s found in tinted clay, it has another name as well: ocher.”
    Frost said, “Isn’t that, like, what American Indians used to paint their faces?”
    “Ocher has been used by mankind for at least three hundred thousand years. It’s even been found in Neanderthal graves. Red ocher in particular seems to have been universally valued in death ceremonies, probably because of its similarity to blood. It’s found in Stone Age cave paintings and on walls in Pompeii. It was used by the ancients to color their bodies as decoration or war paint. And it was used in magical rituals.”
    “Including satanic ceremonies?”
    “It’s the color of blood. Whatever your religion, that color has symbolic power.” Erin paused. “This killer makes quite unusual choices.”
    “I think we already know that,” said Jane.
    “What I mean is, he’s in touch with history. He doesn’t use common chalk for his ritual drawings. Instead he uses the same primitive pigment that was used in the Paleolithic era. And he didn’t just dig it up in his own backyard.”
    “But you said that red ocher is found in common clay,” said Frost. “So maybe he did dig it up.”
    “Not if his backyard is anywhere around here.” Erin nodded at the file folder Jane was holding. “Check out the chemical analysis. What we found on gas chromatography and Raman spectroscopy.”
    Jane flipped to the next page and saw a computer printout. A graph with multiple spikes. “You want to interpret this for us?”
    “Sure. First, the Raman spectroscopy.”
    “Never heard of it.”
    “It’s an archaeologist’s technique for analysis of historic artifacts. It uses the light spectrum of a substance to determine its properties. The big advantage for archaeologists is that it doesn’t destroy the artifact itself. You can analyze the pigments on everything from mummy wrappings to the Shroud of Turin and not damage the article in any way. I asked Dr. Ian MacAvoy, from the Harvard archaeology department, to analyze the Raman spectra results, and he confirmed that the sample contains iron oxide plus clay plus silica.”
    “That’s red ocher?”
    “Yes. Red ocher.”
    “But you already knew that.”
    “Still, it was nice to have him confirm it. Then Dr. MacAvoy offered to help me track down its source. Where in the world this particular red ocher came from.”
    “You can actually do that?”
    “The technique’s still in its research stages. It probably wouldn’t hold up in court as evidence. But he was curious enough to run a comparison against a library of ocher profiles he’s compiled from around the world. He determines the concentrations of eleven other elements in the samples, such as magnesium, titanium, and thorium. The theory is, a particular geographic source will have a distinctive trace element profile. It’s like looking at soil samples from a car tire and knowing that it has the lead-zinc profile of a mining district in Missouri. In this case, with this ocher, we’re checking the sample against eleven separate variables.”
    “Those other trace elements.”
    “Right. And archaeologists have compiled a library of ocher sources.”
    “Why?”
    “Because it helps determine the provenance of an artifact. For instance, where did the pigment on the Shroud of Turin come from? Was it France or Israel? The answer may establish the shroud’s origins. Or an ancient cave painting—where did the artist get his ocher? If it came from a thousand miles away, it tells you that either he’s