CALCITE PREHNITE QUARTZ BRANDBERG
A specimen of Calcite Prehnite Quartz Brandberg on matrix. Specimen featuring good crystal formation and displays well on three cut faces. Interesting and a good representation of minerals. Large enough to be a feature piece.
12.8cm x 7cm x 7.5cm, 612g.
Ca2 Al2 Si3 O10(OH)2
Calcium Aluminum Silicate Hydroxide.
Prehnite is often found with zeolites and is sometimes thought of as a zeolite. But zeolites are actually Tectosilicates and Prehnite is a member the Phyllosilicates Subclass. Like zeolites, Prehnite can give off water when heated, but can not gain the water back like they can.
Its colour is a pleasant green and is at times quite unique to Prehnite. Some Minerals that can be confused with Prehnite include Gyrolite, Smithsonite and Hemimorphite. Prehnite is harder than all of these and lacks Smithsonite’s unusual luster. Hemimorphite is usually blue and Gyrolite is not as glassy.