Jayne had been right. In a little over an hour Mal parked the Mule under the towering rocks known as Huo Yan Shan , or the Mountain of Flames.

“You think they were just being poetical on account of its shape, or is there more to it?” he asked, staring up at the heights as Jayne scouted around. It did look something like a fire, he considered, if he squinted and put his head on one side. Something massive must have hit here, or there was intense seismic activity at some time in the past, maybe during terraforming, but whatever it was had pushed huge plates of base rock up into the sky, where the incessant wind had scoured the softer elements from it, leaving splinter points all along the edges.

“Probably a touch of both,” Freya said, bending down and picking up a scrap of something sharp, the hard shine catching her eye in the sun. “Obsidian,” she added, running her thumb across it, feeling the edge scraping at her skin. “It only gets created in very high temperatures.”

“Volcanic eruptions,” River supplied. “Polymerized lava,” she went on. “No crystal growth.”

“Right,” Mal said, as if he’d understood every word.

“Actually, River’s right,” Simon put in. “And because of the way it’s formed obsidian has been used to make scalpel blades of almost molecular thickness.”

“Just what I needed to know.”

Freya smiled, tossing the chip towards the doctor. “Present for you then, Simon.”

The young man let it fall to the ground before picking it up, as always wary of damaging the fingers that so often had to dig bullets out of the crew. “Thank you so much,” he said witheringly.

Mal’s lips twitched. “If you don’t want it, I'm sure Bethie’ll take it off your hands for you.”

Simon shook his head, well aware of the magpie-ish collecting tendencies of his eldest daughter. “Please, don’t encourage her.”

“I don’t think she needs any encouragement.”

“Mal.” Jayne had reappeared and was pointing towards the base of the rock formation.

“Cave?” Mal asked, looking at Freya.

“Cave