Sapphire (Synthetic Star) | Gemopedia

Synthetic star sapphire exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. The flame fusion process for creating gems, also called the Verneuil process, is the most affordable and common synthesis method for producing corundum (ruby and sapphire) and spinel. Powdered chemicals (the building blocks of the gem) are dropped through a high-temperature flame. The molten powder repeatedly falls from the flame onto a rotating pedestal, creating a synthetic crystal, called a boule, which can later be faceted into a gemstone. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Alternate
Names
Lab Created Star Sapphire
Colors
Light To Dark Violet, Bluish Violet, Blue To Greenish Blue, Brown, Gray, White; All Colors Other Than Blue Need To Be Designated By Color

Sapphire (Synthetic Star) Classification

Common Name

Sapphire (Synthetic Star)

Species

Corundum

Variety

Flame-Fusion Synthetic Star Sapphire

Colors

Light To Dark Violet, Bluish Violet, Blue To Greenish Blue, Brown, Gray, White; All Colors Other Than Blue Need To Be Designated By Color

Alternate Names

Lab Created Star Sapphire

Gemstone Groups

Key Separations

Magnification, appearance and RI

Comments

Stones typically have flat bases and are well cut calibrated cabochons. Stones will have brighter colors than natural sapphire.

Sapphire (Synthetic Star) Optical Properties

Transparency

Semitransparent - Opaque

Refractive Index

1.762-1.77
Tolerance:(+0.009/-0.005)

Birefringence

0.008-0.01

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: inert to moderate chalky blue to yellowish green
LWUV: Inert

CCF Reaction

Pleochroism

Unobservable

Dispersion

Strength: weak fire Value: 0.018

Comments

Sapphire (Synthetic Star) Chemistry & Crystallography

Chemical Name

aluminum oxide

Chemical Formula

Al2O3

Synthesis

flame fusion

Crystal System

Trigonal

Classification

Oxide

Nature

Synthetic

Crystallinity

Crystalline

Comments

Sapphire (Synthetic Star) Characteristic Physical Properties

Hardness

9

Streak

White

Specific Gravity

4.1-3.95 Typical:4

Toughness

Excellent

Inclusions

Flame fusion stones might display curved growth and a unusually display a centered and well defined 6-rayed star. The curved growth is especially visible on the flat base of the stone. The stones might have gas bubbles and minute rutile needles that make up the star will confined to the surface of the stones.

Luster

SubAdamantine

Stability

Very Good

Fracture

Conchoidal

Cleavage

None

Comments

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