TY - JOUR
T1 - Johnkoivulaite, Cs(Be2B)Mg2Si6O18, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar
AU - Palke, Aaron C.
AU - Henling, Lawrence M.
AU - Ma, Chi
AU - Rossman, George R.
AU - Sun, Ziyin
AU - Renfro, Nathan
AU - Kampf, Anthony R.
AU - Thu, Kyaw
AU - Myo, Nay
AU - Wongrawang, Patcharee
AU - Weeramonkhonlert, Vararut
N1 - Publisher Copyright:
© 2021 Mineralogical Society of America.
PY - 2021/11/25
Y1 - 2021/11/25
N2 - A new mineral of the beryl group, johnkoivulaite, Cs(Be2B)Mg2Si6O18, was recovered from the gem gravels in the Pein Pyit area of the Mogok region in Myanmar. Thus far, only a single crystal has been identified. It has dimensions of about 5.8 × 5.7 × 5.5 mm. This specimen has an irregular shape but still has discernible crystal form with geometric growth patterns observed on the crystal faces. The crystal of johnkoivulaite is grayish-violet in color and strongly pleochroic, going from nearly colorless with E⊥c to dark bluish-violet with E||c. Johnkoivulaite has a Mohs hardness of about 7½ and a measured density of 3.01(10) g/cm3. It is uniaxial (-) with ω = 1.607(1) and ϵ = 1.605(1) (white light). Electron microprobe analyses gave the empirical formula of (Cs0.85K0.10Na0.01)(Be1.88B1.12)(Mg1.66Fe0.27Mn0.01Al0.05) (Si5.98)O18 with Be calculated by stoichiometry and confirmed by LA-ICP-MS measurements. Johnkoivulaite is hexagonal, P6/mmc (no. 192) with a = 9.469(2), c = 9.033(2) Å, V = 701.5(3) Å3, and Z = 2. Johnkoivulaite is isostructural with beryl and exhibits partial substitution of B for Be at the distorted tetrahedral site, Mg for Al at the octahedral site, and Cs in the channel sites within the stacked Si6O18 rings. This substitution can be written as (CsMg2B)(□Al2Be)-1. Johnkoivulaite, the seventh member of the beryl group, is named in honor of gemologist John Koivula in recognition of his contributions to mineralogy and gemology.
AB - A new mineral of the beryl group, johnkoivulaite, Cs(Be2B)Mg2Si6O18, was recovered from the gem gravels in the Pein Pyit area of the Mogok region in Myanmar. Thus far, only a single crystal has been identified. It has dimensions of about 5.8 × 5.7 × 5.5 mm. This specimen has an irregular shape but still has discernible crystal form with geometric growth patterns observed on the crystal faces. The crystal of johnkoivulaite is grayish-violet in color and strongly pleochroic, going from nearly colorless with E⊥c to dark bluish-violet with E||c. Johnkoivulaite has a Mohs hardness of about 7½ and a measured density of 3.01(10) g/cm3. It is uniaxial (-) with ω = 1.607(1) and ϵ = 1.605(1) (white light). Electron microprobe analyses gave the empirical formula of (Cs0.85K0.10Na0.01)(Be1.88B1.12)(Mg1.66Fe0.27Mn0.01Al0.05) (Si5.98)O18 with Be calculated by stoichiometry and confirmed by LA-ICP-MS measurements. Johnkoivulaite is hexagonal, P6/mmc (no. 192) with a = 9.469(2), c = 9.033(2) Å, V = 701.5(3) Å3, and Z = 2. Johnkoivulaite is isostructural with beryl and exhibits partial substitution of B for Be at the distorted tetrahedral site, Mg for Al at the octahedral site, and Cs in the channel sites within the stacked Si6O18 rings. This substitution can be written as (CsMg2B)(□Al2Be)-1. Johnkoivulaite, the seventh member of the beryl group, is named in honor of gemologist John Koivula in recognition of his contributions to mineralogy and gemology.
UR - http://www.scopus.com/inward/record.url?scp=85119154036&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85119154036&partnerID=8YFLogxK
U2 - 10.2138/am-2021-7785
DO - 10.2138/am-2021-7785
M3 - Article
AN - SCOPUS:85119154036
SN - 0003-004X
VL - 106
SP - 1844
EP - 1851
JO - American Mineralogist
JF - American Mineralogist
IS - 11
ER -