- journal_title：The Canadian Mineralogist
- Contributor：Jinru Lin ; Yuanming Pan ; Ning Chen ; Mao Mao ; Rong Li ; Renfei Feng
- Publisher：Mineralogical Association of Canada
- Date：2011-
- Format：text/html
- Language：en
- Identifier：10.3749/canmin.49.3.809
- journal_abbrev：Can Mineral
- issn：0008-4476
- volume：49
- issue：3
- firstpage：809
- section：Articles
World-class borate deposits in Turkey and California contain elevated concentrations of arsenic, with adverse effects to not only local suppliers of water, but also the commercial exports of boron products. Most previous studies and remediation efforts of arsenic contamination in borate deposits have focused on sulfarsenides. Inductively coupled plasma – mass spectrometry (ICP–MS) analysis and synchrotron micro-X-ray fluorescence (μ-SXRF) mapping reveal that colemanite, a major borate ore mineral, contains up to 125 ppm arsenic. Arsenic K-edge X-ray absorption near-edge structure (XANES) spectra suggest the presence of both As3+ and As5+ species in colemanite. The data on K-edge extended X-ray absorption fine structure (EXAFS) show preferential occupancies of As5+ and As3+ at the tetrahedral B2 site and the triangular B1 site, respectively. Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated colemanite measured at 40 K contain an [AsO3]2− center, providing further support for the presence of As5+. Therefore, colemanite is a significant source of arsenic contamination, not only in commercial boron products, but also aquifers associated with borate deposits.