The structures of three B-substituted albite samples (NaBSi3O8), including reedmergnerite from Utah and low and high synthetic boron albite, have been refined at room temperature with single-crystal X-ray intensities. For reedmergnerite, R = 0.019, the structure is ideally ordored with B in the T10 site, and the electron density distribution at the Na position is anisotropic as in low albite and low gallium albite. Average T-O distances are T10 [1.472(1)], T1m [1.611(1)], T2O [1.615(1)], T2m [1.619(1) Å]. The structure of low boron albite refined to R = 0.027. Average T-O distances and B site occupancies are T1O [1.497(2), 0.805(1)], T1m [1.606(1), 0.014(1)], T2O [1.593(1), 0.135(1)], T2m [1.610(1) Å, 0.046(1)]. The structure of high boron albite refined similarly to R = 0.037, T1O [1.571(2), 0.289(3)], T1m [1.598(2), 0.058(3)], T2O [1.553(2), 0.384(3)], T2m [1.574(2) Å, 0.269(3)].

Average T-O distances for reedmergnerite and boron albite exhibit an almost linear correlation with site occupancies of B (tiB). The tetrahedral-site ordering sequences of t1O ≫ t2O ≫ t2m > t1m in low boron albite and t2O > t1O ≈ t2m > t1m in high boron albite are very unusual compared with albite but do correlate with stereochemical features. High boron albite is antiordered with (t1O + t1m) < (t2O + t2m). The order-disorder transformation in boron albite appears to occur within the temperature range 500–550°C at PH2O ≈ 1 kbar.

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