Adularia | Gemopedia

Adularia is a variety of feldspar found in hydrothermal veins in mountainous areas, from one of which it derives its name: the Adular Mountains of Switzerland. It commonly forms colorless to white, cream, pale yellow to pink, or reddish-brown, glassy, prismatic, twinned crystals. These transparent to colorless gems often display a white to blue sheen.
Colors
Colorless With White, Blue Sheen

Adularia Classification

Common Name

Adularia

Species

Orthoclase

Variety

Adularia

Colors

Colorless With White, Blue Sheen

Alternate Names

Gemstone Groups

Feldspar

Key Separations

refractive index, birefringence, optic character and possibly spectrum and fluorescence

Comments

This stone comes from Adula mountains in Switzerland and this is where the phenomena adularescence gets its name.

Adularia Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.518-1.526
Tolerance:(+0.010/-)0.010)

Birefringence

0.005-0.008

Optic Character

Biaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak orangy red
LWUV: Inert to weak blue or pink

CCF Reaction

Pleochroism

Unobservable

Dispersion

Strength: weak fire Value: 0.12

Comments

Adularia Chemistry & Crystallography

Chemical Name

potassium aluminum silicate

Chemical Formula

KAlSi3O8

Synthesis

Crystal System

Monoclinic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Adularia Characteristic Physical Properties

Hardness

6

Streak

White

Specific Gravity

2.55-2.61 Typical:2.58

Toughness

Inclusions

Adularia will display white or blue adularescence. Stones might have centipede like inclusions and material with aventuresence or asterism might contain reflective inclusions such as fine needles or elongated hematite platelets.

Luster

Vitreous

Stability

Fracture

Uneven, Splintery

Cleavage

Perfect, in two directions

Comments

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