The Dom Pedro Crystal
The Dom Pedro gem superimposed on the original crystal. Photo courtesy of B. Munsteiner.
The mineral beryl is a beryllium aluminum silicate that is colorless in its pure form. The rich hues of its gem varieties are caused by impurity atoms that were incorporated in the crystal as it grew. These trace elements are responsible for the colorful varieties of beryl: blue aquamarine, green emerald, pink morganite and yellow heliodore. Aquamarine, as the name suggests, exhibits the variable color of the sea. It is the presence of iron that causes the blue to blue-green color of this gem.
Beryl can form very large crystals and quite often with few inclusions. However, characteristic of many aquamarines are hollow tube inclusions that formed during the crystal’s growth. They are elongated growth ducts that are aligned parallel to the main crystal axis, or c-axis. They are typically voids and elongated negative crystals filled with either liquid and gas bubbles or foreign crystals. In long prismatic aquamarine crystals, small pieces of mineral matter or liquid droplets can fall on the growing crystal face. The beryl crystal grows so rapidly in the c-axis direction that a tube forms and grows and extends, sometimes to great lengths, without the walls of the tube growing together. Eventually there is a gradual closing of the walls until the hollow tube inclusion resembles an elongated rain-drop.
Some beryl crystals exhibit zones of clean material interspersed with zones containing these tubular inclusions. In the case of the Dom Pedro, the crystal was fairly free of inclusions near the base but contains many of these hollow tube inclusions near the termination or top of the crystal. Bernd Munsteiner, the artist and master gem-carver, decided to incorporate these inclusions in the design of the sculpture, as seen at the base of the obelisk.
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