Johnkoivulaite, Cs(Be2B)Mg2Si6O18, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar

Aaron C. Palke, Lawrence M. Henling, Chi Ma, George R. Rossman, Ziyin Sun, Nathan Renfro, Anthony R. Kampf, Kyaw Thu, Nay Myo, Patcharee Wongrawang, Vararut Weeramonkhonlert

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)1844-1851
Number of pages8
JournalAmerican Mineralogist
Volume106
Issue number11
DOIs
Publication statusPublished - Nov 25 2021

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Fingerprint

Dive into the research topics of 'Johnkoivulaite, Cs(Be<sub>2</sub>B)Mg<sub>2</sub>Si<sub>6</sub>O<sub>18</sub>, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar'. Together they form a unique fingerprint.

Cite this