Beryl

Properties

Chemical Composition: Beryllium Aluminium Silicate (Be₃Al₂(SiO₃)6; Trace elements are Cr, V, Fe, Mn, etc.

Classification / Type: -

Colors / Varieties: 

• Green - Emerald (Cr/V/Fe)
• Green - Green Beryl (No Chromium)
• Colorless - Goshenite
• Blue - Aquamarine
• Yellow - Yellow Beryl
• Golden - Heliodor
• Pink - Morganite
• Red - Red Beryl
• Deep blue (fading) - Maxixe Beryl
• Chatoyant - Cat's eye beryl
• Asteriated - Star beryl
• Parti-colored beryl
• Trapiche emerald - green with black spokes intersecting.

Crystal System / Forms: Hexagonal System / Generally as six-sided prisms with pyramidal and / or pinacoidal terminations. As such columnar prismatic habits are common.

Hardness: 7.5 - 8

Specific Gravity: 2.68 - 2.80

Cleavage / Fracture: Poor cleavage / parting parallel to the basal plane.

Optic Character: Anisotropic, D.R.; Uniaxial Negative.

Lustre: Vitreous.

Refractive Index / Birefringence: 1.577 - 1.583 / 0.006 - 0.009. R.I. Range: 1.57 - 1.60

Pleochroism: Distinct dichroism depending on depth of color.

Dispersion: 0.014

Magnification: Parallel two phase or rain inclusions, three phase and crystalline inclusions, fingerprints, hexagonal growth zoning.

U.V. Fluorescence: Variable.

Spectrum: 

• Fading blue maxixe beryl: bands at 695nm & 655nm with weaker bands at 628nm, 615nm, 581nm and 550nm.
• Green and yellow beryl, pink beryl: spectrum is not well pronounced.

Cause of Color: 

• Green and yellow beryl: Fe %
• Morganite: Mn with traces of cesium and rubidium. (Presence increases the physical and optical constants).
• Maxixe blue beryl: unstable color center

Treatment (Enhancement): 

• Coating: colored coatings to improve color
• Colorless impregnation: oil / resin to improve clarity
• Colored impregnation: dyes / resin to improve clarity and color
• Heat Treatment (except on emerald): lime green color to aquamarine blue; improves pink in morganite
• Irradiation: Colorless to yellow.

Specific Tests & Remarks: -

Simulants (with key separation tests): Yellow beryl: Citrine (optic figure, R.I.), Scapolite (R.I., birefringence, U.V. fluorescence, doubling), glass (optic character), hessonite garnet (R.I., S.G., inclusions), Topaz (R.I., S.G.), Labradorite (R.I., inclusions, U.V. fluorescence), Sillimanite (R.I., S.G., inclusions).

Geological Occurrence: Granitic rocks - pegmatite and schists, in hydrothermal veins and metamorphic limestone.

Sources: Morganite: Madagascar, U.S.A. (California, Utah), India (Orissa), Pakistan.

Cuts & Uses: Facetted cuts, cabochons, beads, carvings, etc.