Dark Blue Aquamarine form the True Blue Showing, Yukon Territory



LEE A. GROAT and DAVID J. TURNER
Department of Earth and Ocean Sciences, University of British Columbia,
Vancouver, British Columbia V6T 1Z4

GEORGE R. ROSSMAN
Division of Geological and Planetary Sciences, California Institute of Technology,
Pasadena, California 91125-2500, U.S.A.

ABSTRACT

Dark blue aquamarine was discovered in the Yukon Territory in 2003.  The crystals occur in a swarm of quartz ± siderite ± fluorite ± allanite veins that fill tension gashes in a syenite stock.  Previous studies suggest a metamorphic origin for the mineralizing fluid and local derivation of vein constituents.  The dark blue beryl contains nearly 6.0 wt.% FeO and the colour is thought to be due to intervalence charge-transfer between Fe2+ and Fe3+ cations.  Five stones weighing up to 0.82 carats were faceted in 2003, but these are heavily fractured and included.  However, many of the smaller crystals discovered to date are transparent.