Birefringence

Delphi's eyes shimmered as they adjusted to the alien light. Far overhead, a quartz crystal flooded the cavern with circularly polarized energy. Delphi squirmed, laughing as the light penetrated through her thin, fiber cladding. The resulting interference patterns stimulated her inner sensors; it tickled.

"Different, huh?" asked Cruv, his milky figure appearing at her side.

"When did you install it?" asked Delphi, trying not to stare at his emaciated form, his unpolished chest, or the way his face had become pockmarked with impurities.

"Three years ago, after the last litter left for the surface,” Cruv replied. “Remember those crystals we used to fish out of the mantle plumes?"

Delphi nodded. "Sure. Polished gemstones. Quartz as clear as water. The kids would break them up into tiny slivers, savoring every chip." Her skin glowed, phosphorescing at the memory.

Cruv laughed. "Well, I guess we never appreciated just how fast the crystals grew." He gestured upward, the rotating light casting spinning shadows on the cavern wall. "It took only the barest cultivation. Perfect birefringence. Could barely haul it out of the mantle. If I had waited a week longer, quartz would have blocked the plume all together."

Delphi shook her head, frowning. "And then? What would you mineralize?" she asked. "You'd waste away.” She paused. “More than you have already.”

"Never gave it much thought." Cruv's voice softened. "To be honest, after you left, I stopped business. Mineralization, refining, polishing. The stalagmite forest grew wild for a year."

Delphi turned her eyes away from Cruv's cloudy body. Overhead, light refracted through the quartz, forming fringe patterns—a melody of constructive and destructive waves. Delphi's eyes listened to the song.

"Delphi..." whispered Cruv.

"I'm sorry," she said, "They...they made an offer. I only came to say goodbye. I’m leaving for the surface."