Ethiopian Opal | Gemopedia

Opal with play of color has always been considered one of the most desired gems in the marketplace, earning it the undisputed title as 'Queen of Gemstones'. With the discovery of precious (and stable) opal in Ethiopia's northern Welo District in 2008, coupled with its prolific bounty, this remarkable gem has reclaimed its throne and rules again as one of the most in-demand gemstones in the 21st century.
Colors
Colorless, White, Yellow, Orange, Brown

Ethiopian Opal Classification

Common Name

Ethiopian Opal

Species

Opal

Variety

Ethiopian Opal

Colors

Colorless, White, Yellow, Orange, Brown

Alternate Names

Gemstone Groups

Key Separations

Key tests are play-of-color, refractive index and fluorescence. Opals might phosphoresce, and this is a strong indication of its natural origins, as synthetic or simulant opals do not phosphoresce.

Comments

Many Ethiopian opals are hydrophane opal which is porous and will take on water. The SG of stones can be variable due to soaking in liquid or due to the humidity of surrounding atmosphere.

Ethiopian Opal Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.45
Tolerance:-0.25

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Singly Refractive (SR) With ADR

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

None

Dispersion

Strength: none

Comments

Ethiopian Opal Chemistry & Crystallography

Chemical Name

silica

Chemical Formula

SiO2-nH2O

Synthesis

Crystal System

NA

Classification

Silicate

Nature

Natural

Crystallinity

Polycrystalline

Comments

Ethiopian Opal Characteristic Physical Properties

Hardness

5-6.5

Streak

White

Specific Gravity

1.25-2.23 Typical:2.15

Toughness

Varies

Inclusions

Ethiopian opal will have play-of-color in various patterns, such as pinfire (small patches or dots), flash (large areas of color), harlequin (brush-strokes of color); flagstone and other unique patterns.

Luster

Vitreous

Stability

Poor

Fracture

Conchoidal, Uneven

Cleavage

None

Comments

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