LARGE MINERAL SPECIMEN OF CALCITE PSEUDO. @ NAHCOLITE, GREEN RIVER BASIN, WY

Description

THIS IS A LARGE SPECIMEN OF A
CALCITE PSEUDOMORPH AFTER NAHCOLITE IN SHALE.
THE SPECIMEN IS
APPROXIMATELY 17 X 12 X 3 cm
.  AND
WEIGHS ABOUT 1.5 LBS
.  THE
DIAMETER OF THE CALCITE PSEUDOMORPH IS ABOUT 3 cm
.  THERE FOUR OTHER, SMALLER PSEUDOMORPHS ON THE SPECIMEN.  IT IS FROM
GREEN RIVER, SWEETWATER CO., WYOMING.
THIS IS AN UNUSUAL PSEUDOMORPH.  THE NAHCOLITE ORIGINALLY FORMED CRYSTALLINE BALLS IN THE MUD THAT LATER BECAME SHALE.  THE NAHCOLITE WAS REPLACED BY CALCITE.  THIS OCCURS IN THE GREEN RIVER FORMATION, EOCENE EPOCH.  THE GREEN RIVER DEPOSIT IS THE WORLDS LARGEST KNOWN TRONA DEPOSIT.  IT DISPLAYS VERY WELL.  IT WAS COLLECTED IN 1989.  SEE PICTURES.  I WILL COMBINE SHIPPING WHEN POSSIBLE.  THANKS FOR LOOKING.