Heulandite

Heulandite is a collective term for those recognized by the IMA minerals heulandite - Ba, Heulandite Ca, heulandite -K, heulandite -Na, heulandite -Sr.

These individual minerals are the respective end members of a mineral series the following chemical composition:

  • Heulandite -Ba - NaBa4 ( Si27Al9 ) O72 • 24H2O
  • Heulandites -Ca - NaCa4 ( Si27Al9 ) O72 • 24H2O
  • Heulandites -K - KCa4 ( Si27Al9 ) O72 • 24H2O
  • Heulandites -Na - (Na, Ca) 6 (Si, Al) 36O72 • 24H2O
  • Heulandites -Sr NaSr4 ( Si27Al9 ) O72 • 24H2O

Special Features

All heulandites crystallize in monoklischen crystal system and develop usually prismatic or tabular crystals, but also granular to massive aggregates, which are colored either colorless or white. Impurities some heulandites also accept a gray, brownish, yellowish, reddish or greenish color.

Classification

After the now outdated nomenclature of minerals according to Strunz ( 8th edition ) the heulandites associated with the framework silicates ( tectosilicates ) and members of the zeolite group, or more precisely the Blätterzeolithen with the system no. VIII/J.23-06 ( heulandite -Na) to VIII/J.23-14 ( heulandite - Ba).

In the new classification of minerals according to Strunz ( 9th edition ) you can still find the heulandites under the same framework silicates, however, in the subdivision of the "family of zeolites with zeolitischem H2O and tafeliger 4-4-1-1- structure." Together with the clinoptilolite they got the system no. 9.GE.05.

After the classification of minerals according to the Dana heulandites are also assigned to the framework silicates and associated with the clinoptilolite the department 77.1.4 ( heulandites and related species).

List of minerals
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