MINERALIZATION

The quartz-calcite-beryl mineralization is hydrothermal, originating from granodiorite, which runs the full length of the talc schist. The chromium necessary for the emerald coloration was probably contained in the ascending solution as it passed through the ultramafic rocks that have been altered in serpentinites. Emeralds occur also in pockets associated with veins of quartz, calcite and talc. The emeralds found in quartz usually are broken whereas those found in carbonate-talc schist are normally intact and euhedral.

(Euhedral refers to well-formed crystals with sharp, easily-recognized faces. Normally, crystals do not form smooth faces or sharp crystal outlines. Many crystals grow from cooling liquid magma. As magma cools, the crystals grow, and they eventually touch each other, preventing crystal faces form forming properly or at all.

(However, when snowflakes crystallize, they do not touch each other. Thus, snowflakes form euhedral, six-sided twinned crystals. In rocks, the presence of euhedral crystals may signify that they formed early in the crystallization of a magma or perhaps crystallized in a cavity or vug, without hindrance from other crystals.

(Etymology: Euhedral is derived from the Greek hedron meaning shape.)