General formula:

Na2(Fe2+,Mg2+)3Fe3+2Si8O22OH2

N° standard / mount: 007 / Tubes
Standard elements: Fe Na Si
Mineral class: Silicates
Group: Amphiboles
Comments:

Mostly homogeneous, some inclusions SiO2, FeO, …

Analysis:
Riebeckite ENS Analysis
Riebeckite ENS