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Al-Si–rich laboratory spherules made at >1,730 °C. (A) Micrograph of oak spherules; largest = 350 µm. (B) SEM image of same oak spherule group. (C) SEM image of pine spherules; largest = 220 µm. (D) YDB objects ≥200 µm compared with Al-Si–rich oak and pine. Red dashed line represents equivalent values. Data shown are in SI Appendix, Tables S6 and S7.
