measured	value	unit
[SiO₂]	36.6	%
[TiO₂]	0.43	%
[Al₂O₃]	29.4	%
[Cr₂O₃]	2.5	%
[FeO^T]	9.61	%
[NiO]	0.18	%
[MgO]	4.48	%
[Na₂O]	2.42	%

tables:

Table 1-2. 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