Inclusions in synthetic quartz

Synthetic quartz grown in steel autoclaves under standard conditions in Na₂CO₃ solution (with trace Li) traps secondary phase particulates during growth. Identification of these particulates, although difficult due to small size (<5 to 100s of μm), is possible using X-ray diffraction, electron microprobe, and optical microscopic techniques. Four secondary phases were identified in normally grown crystals: Li₂Si₂O₅, NaFeSi₂O₆, Na₅FeSi₄O₁₂, and a phase with estimated composition Li₆Na₆Fe₂Si₁₈ O₄₅. The last three phases are often found together in crystals, which suggests that a stable phase assemblage for quartz growth in steel autoclaves in Na₂CO₃ solution is quartz+fluid+iron oxide+NaFeSi₂O₆+Na₅FeSi₄O₁₂+Li₆Na₆Fe₂Si₁₈O₄₅. Quartz grown in Na₂CO₃ solution with added iron also develops three accessory phases. Quartz grown in silver liners in Li-free carbonate solution traps only NaFeSi₂O₆ and fluid inclusions.