Segerstromite, Ca3(As5+O4)2[As3+(OH)3]2, the first mineral containing As3+(OH)3, the arsenite molecule, from the Cobriza mine in the Atacama Region, Chile

Hexiong Yang; Robert T. Downs; Robert A. Jenkins; Stanley H. Evans

doi:10.2138/am-2018-6329

Segerstromite, Ca₃(As⁵⁺O₄)₂[As³⁺(OH)₃]₂, the first mineral containing As³⁺(OH)₃, the arsenite molecule, from the Cobriza mine in the Atacama Region, Chile

Hexiong Yang
, Robert T. Downs
, Robert A. Jenkins
, Stanley H. Evans

Geosciences

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

A new mineral species, segerstromite, ideally Ca₃(As⁵⁺O₄)₂[As³⁺(OH)₃]₂, has been discovered at the Cobriza mine in the Sacramento district in the Copiapó Province, Chile. Crystals of segerstromite occur as tetrahedra, dodecahedra (up to 0.50 × 0.50 × 0.50 mm), or in blocky aggregates. Associated minerals include talmessite, vladimirite, and Sr-bearing hydroxylapatite. Similar to the associated minerals, segerstromite is a secondary mineral. The new mineral is colorless in transmitted light, transparent with a white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼4.5. No cleavage, parting, or twinning was observed. The measured and calculated densities are 3.44(3) and 3.46 g/cm³, respectively. Optically, segerstromite is isotropic, with n = 1.731(5). It is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula (based on 14 O apfu) Ca_2.98(AsO₄)_2.00[As(OH)₃]_2.00. Segerstromite is cubic, with space group I2₁3 and unit-cell parameters a = 10.7627(2) Å, V = 1246.71(4) Å³, and Z = 4. Its crystal structure is constructed from three different polyhedral units: distorted CaO₈ cubes, rigid As⁵⁺O₄ arsenate tetrahedra, and neutral As³⁺(OH)₃ arsenite triangular pyramids. The Ca-groups form layers of corrugated crankshaft chains that lie parallel to the cubic axes. These chains are linked by the isolated As⁵⁺O₄ and As³⁺(OH)₃ groups. Segerstromite is the first known crystalline compound that contains the As³⁺(OH)₃ arsenite molecule, pointing to a new potential approach to remove highly toxic and mobile As³⁺(OH)₃ from drinking water.

Original language	English (US)
Pages (from-to)	1497-1501
Number of pages	5
Journal	American Mineralogist
Volume	103
Issue number	9
DOIs	https://doi.org/10.2138/am-2018-6329
State	Published - Sep 25 2018

Keywords

New mineral
Raman spectrum
X-ray diffraction
arsenate/arsenite
crystal structure
segerstromite

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology

Access to Document

10.2138/am-2018-6329

Cite this

@article{626d83ee94f141f095e4a423239eb134,

title = "Segerstromite, Ca3(As5+O4)2[As3+(OH)3]2, the first mineral containing As3+(OH)3, the arsenite molecule, from the Cobriza mine in the Atacama Region, Chile",

abstract = "A new mineral species, segerstromite, ideally Ca3(As5+O4)2[As3+(OH)3]2, has been discovered at the Cobriza mine in the Sacramento district in the Copiap{\'o} Province, Chile. Crystals of segerstromite occur as tetrahedra, dodecahedra (up to 0.50 × 0.50 × 0.50 mm), or in blocky aggregates. Associated minerals include talmessite, vladimirite, and Sr-bearing hydroxylapatite. Similar to the associated minerals, segerstromite is a secondary mineral. The new mineral is colorless in transmitted light, transparent with a white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼4.5. No cleavage, parting, or twinning was observed. The measured and calculated densities are 3.44(3) and 3.46 g/cm3, respectively. Optically, segerstromite is isotropic, with n = 1.731(5). It is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula (based on 14 O apfu) Ca2.98(AsO4)2.00[As(OH)3]2.00. Segerstromite is cubic, with space group I213 and unit-cell parameters a = 10.7627(2) {\AA}, V = 1246.71(4) {\AA}3, and Z = 4. Its crystal structure is constructed from three different polyhedral units: distorted CaO8 cubes, rigid As5+O4 arsenate tetrahedra, and neutral As3+(OH)3 arsenite triangular pyramids. The Ca-groups form layers of corrugated crankshaft chains that lie parallel to the cubic axes. These chains are linked by the isolated As5+O4 and As3+(OH)3 groups. Segerstromite is the first known crystalline compound that contains the As3+(OH)3 arsenite molecule, pointing to a new potential approach to remove highly toxic and mobile As3+(OH)3 from drinking water.",

keywords = "New mineral, Raman spectrum, X-ray diffraction, arsenate/arsenite, crystal structure, segerstromite",

author = "Hexiong Yang and Downs, \{Robert T.\} and Jenkins, \{Robert A.\} and Evans, \{Stanley H.\}",

note = "Publisher Copyright: {\textcopyright} 2018 Walter de Gruyter GmbH, Berlin/Boston.",

year = "2018",

month = sep,

day = "25",

doi = "10.2138/am-2018-6329",

language = "English (US)",

volume = "103",

pages = "1497--1501",

journal = "American Mineralogist",

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TY - JOUR

T1 - Segerstromite, Ca3(As5+O4)2[As3+(OH)3]2, the first mineral containing As3+(OH)3, the arsenite molecule, from the Cobriza mine in the Atacama Region, Chile

AU - Yang, Hexiong

AU - Downs, Robert T.

AU - Jenkins, Robert A.

AU - Evans, Stanley H.

PY - 2018/9/25

Y1 - 2018/9/25

N2 - A new mineral species, segerstromite, ideally Ca3(As5+O4)2[As3+(OH)3]2, has been discovered at the Cobriza mine in the Sacramento district in the Copiapó Province, Chile. Crystals of segerstromite occur as tetrahedra, dodecahedra (up to 0.50 × 0.50 × 0.50 mm), or in blocky aggregates. Associated minerals include talmessite, vladimirite, and Sr-bearing hydroxylapatite. Similar to the associated minerals, segerstromite is a secondary mineral. The new mineral is colorless in transmitted light, transparent with a white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼4.5. No cleavage, parting, or twinning was observed. The measured and calculated densities are 3.44(3) and 3.46 g/cm3, respectively. Optically, segerstromite is isotropic, with n = 1.731(5). It is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula (based on 14 O apfu) Ca2.98(AsO4)2.00[As(OH)3]2.00. Segerstromite is cubic, with space group I213 and unit-cell parameters a = 10.7627(2) Å, V = 1246.71(4) Å3, and Z = 4. Its crystal structure is constructed from three different polyhedral units: distorted CaO8 cubes, rigid As5+O4 arsenate tetrahedra, and neutral As3+(OH)3 arsenite triangular pyramids. The Ca-groups form layers of corrugated crankshaft chains that lie parallel to the cubic axes. These chains are linked by the isolated As5+O4 and As3+(OH)3 groups. Segerstromite is the first known crystalline compound that contains the As3+(OH)3 arsenite molecule, pointing to a new potential approach to remove highly toxic and mobile As3+(OH)3 from drinking water.

AB - A new mineral species, segerstromite, ideally Ca3(As5+O4)2[As3+(OH)3]2, has been discovered at the Cobriza mine in the Sacramento district in the Copiapó Province, Chile. Crystals of segerstromite occur as tetrahedra, dodecahedra (up to 0.50 × 0.50 × 0.50 mm), or in blocky aggregates. Associated minerals include talmessite, vladimirite, and Sr-bearing hydroxylapatite. Similar to the associated minerals, segerstromite is a secondary mineral. The new mineral is colorless in transmitted light, transparent with a white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼4.5. No cleavage, parting, or twinning was observed. The measured and calculated densities are 3.44(3) and 3.46 g/cm3, respectively. Optically, segerstromite is isotropic, with n = 1.731(5). It is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula (based on 14 O apfu) Ca2.98(AsO4)2.00[As(OH)3]2.00. Segerstromite is cubic, with space group I213 and unit-cell parameters a = 10.7627(2) Å, V = 1246.71(4) Å3, and Z = 4. Its crystal structure is constructed from three different polyhedral units: distorted CaO8 cubes, rigid As5+O4 arsenate tetrahedra, and neutral As3+(OH)3 arsenite triangular pyramids. The Ca-groups form layers of corrugated crankshaft chains that lie parallel to the cubic axes. These chains are linked by the isolated As5+O4 and As3+(OH)3 groups. Segerstromite is the first known crystalline compound that contains the As3+(OH)3 arsenite molecule, pointing to a new potential approach to remove highly toxic and mobile As3+(OH)3 from drinking water.

KW - New mineral

KW - Raman spectrum

KW - X-ray diffraction

KW - arsenate/arsenite

KW - crystal structure

KW - segerstromite

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UR - https://www.scopus.com/pages/publications/85053289514#tab=citedBy

U2 - 10.2138/am-2018-6329

DO - 10.2138/am-2018-6329

M3 - Article

AN - SCOPUS:85053289514

SN - 0003-004X

VL - 103

SP - 1497

EP - 1501

JO - American Mineralogist

JF - American Mineralogist

IS - 9

ER -