measured	value	unit
[SiO₂]	36.1	%
[TiO₂]	1.51	%
[Al₂O₃]	29.9	%
[Cr₂O₃]	0.12	%
[FeO^T]	10.7	%
[NiO]	0.16	%
[MgO]	4.96	%
[CaO]	0.17	%
[Na₂O]	2.28	%

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