Photo: Robert M. Lavinsky · CC BY-SA 3.0

Na-amphibole, double chain inosilicate mineral

Properties

Chemical formula

☐Na₂(Fe²⁺₃Fe³⁺₂)Si₂O₂₂(OH)₂

Group

Silicates

Crystal system

Monoclinic

Hardness (Mohs)

6

Color

Black

Luster

—

Streak

—

Density

—

Cleavage

—

Fracture

—

Tenacity

—

Crystal habit

—

Transparency

—

Space group

C2/m

Fluorescence

—

Magnetism

—

Radioactivity

—

Refractive index

—

Optical character

—

Birefringence

—

Pleochroism

—

Strunz classification

9.DE.25

Dana classification

—

IMA status

Redefined mineral (Rd)

IMA symbol

Rbk

Locality

🇾🇪 Socotra

Type locality

—

Discovery year

—

Source: Wikidata