Crystal Sunset Feldspar

Chemical Formula

Na₈Al₆Si₆O₂₄Cl₂

Composition

Sodium aluminum silicate with chlorine, and occasionally sulfur.
 

Variable Formula

Na₈Al₆Si₆O₂₄(Cl₂,S)

Color

Most often blue, less commonly purple, pink, gray, green, brown, white, and colorless. May also be multicolored blue with white and gray veins.

Streak

White

Hardness

5.5 - 6

Crystal System

Isometric

Crystal Forms 
and Aggregates

Crystals, which are dodecahedral, are rare and will usually have complex or rounded terminations. Most often massive, grainy, and nodular.
 

Transparency

Transparent to opaque

Specific Gravity

2.2 - 2.3

Luster

Vitreous to greasy; may also be dull.

Cleavage

3,6

Fracture

Uneven

Tenacity

Brittle

Other ID Marks

Often fluorescent a creamy-white, yellow, or orange color in shortwave ultraviolet light. The varietyHackmanite fluoresces orange to red in shortwave, and orange in longwave.
 

In Group

Silicates; Tectosilicates; Feldspathoid Group

Striking Features

Habitual deep blue color

Environment

Sodalites occur in a variety of different environments, including alkaline nepheline syenite pegmatites,metamorphosed marbles and skarns, and both intrusive and extrusive igneous rock.

Rock Type

Igneous, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

2

Demand (1-3)

2