calcite - teaching hand/display specimen of massive naturally-brown calcite Aragonite-based scleractinian corals replaced the

Aragonite-based scleractinian corals replaced the calcite-based tabulate reef building corals during the Permo-Triassic extinction event roughly 252 million years ago

the partly dried perlite is heated to 1

This type of chert is a sedimentary rock

The frosted quartz grains are characteristic of the Navajo Sandstone - the quartz grains essentially sandblasted each other as they were transported by the wind and deposited in dunes

This genus was erected by Jacob Hübner in 1819

calcite - teaching hand/display specimen of massive naturally-brown calcite Aragonite-based scleractinian corals replaced theThis calcite is recrystallized from a limestone in contact with a granitic intrusion. The brown color is unusual and is derived from iron in the limestone that was released by the metamorphism. It effervesces in dilute hydrochloric acid (muriatic acid is the same) as does all calcite. The crystals of this calcite are interlocking, so it does not cleave into large rhombs, though individual specimens show many cleavage faces in several directions. The