calcite - cool pink fluorescent and phosphorescent calcite - cleavage rhomb from the Challenger Cave system, Nuevo Leon, Mexico This medium-grained sandstone is composed

This medium-grained sandstone is composed primarily of quartz with feldspar and some biotite

The pen is 5" long

The mineral was called "cyanite" by mineralogists using the French spelling

Locally it is poorly to moderately well cemented with silica cement

The Navajo sandstone is widely  exposed in southern Utah and forms the colorful crossbedded cliffs at Zion National Park

calcite - cool pink fluorescent and phosphorescent calcite - cleavage rhomb from the Challenger Cave system, Nuevo Leon, Mexico This medium-grained sandstone is composedCalcite, CaCO3, is an extremely common rock forming mineral. In pegmatites it forms large masses and it makes up some limestones almost entirely. It has a large variety of crystal forms, but these do not include the rhombus shaped pieces that are sold as calcite crystals. The rhombs are produced by cleaving calcite in three directions between rows of atoms. When calcite is free of impurities and is optically clear, it exhibits double refraction. When