measured	value	unit
[SiO₂]	36.4	%
[TiO₂]	0.42	%
[Al₂O₃]	31.8	%
[Cr₂O₃]	0.12	%
[FeO^T]	9.6	%
[NiO]	0.38	%
[MgO]	4.79	%
[Na₂O]	2.18	%

tables:

Table 1-1. Chemical compositions of tourmaline.Elemental abundances are normalized to a total of 100 cg/g of Ota, Tsutomu (2019) Tourmaline in a Mesoarchean pelagic hydrothermal system: Implications for the habitat of early life, Precambrian Research, 334. more