BerylBeryl

BerylBeryl Aqua marineAqua marine

EmeraldEmerald GosheniteGoshenite

HeliodorHeliodor

MorganiteMorganite

Emerald: green varietyEmerald: green variety

The varieties of berylThe varieties of beryl

Beryl: golden or red varietyBeryl: golden or red variety

Morganite: pink variety Morganite: pink variety

Aquamarine: blue varietyAquamarine: blue variety

Heliodor: greenish-yellow varietyHeliodor: greenish-yellow variety

Goshenite: colourless varietyGoshenite: colourless variety

Interesting history:Interesting history: - Emeralds were mined in ancient Egypt 4000 years ago- Emeralds were mined in ancient Egypt 4000 years ago

- In the 1600’s, high quality emerald reached Europe.- In the 1600’s, high quality emerald reached Europe.

- The Spaniards seized the emeralds from the - The Spaniards seized the emeralds from the Pre-Colombian people.Pre-Colombian people.

- Mining in Colombia is still going on today, and often - Mining in Colombia is still going on today, and often associated with criminal activities.associated with criminal activities.

The physical properties of berylThe physical properties of beryl

Luster: vitreous, transparent to translucent Luster: vitreous, transparent to translucent

Cleavage: imperfect in one direction, conchoidal fractureCleavage: imperfect in one direction, conchoidal fracture

Hardness: 7.5 - 8Hardness: 7.5 - 8

Specific gravity: 2.6 – 2.9 on averageSpecific gravity: 2.6 – 2.9 on average

Crystal habit: hexagonal prism with pincoid terminationCrystal habit: hexagonal prism with pincoid termination

Group: beryl is a cyclosilicate Group: beryl is a cyclosilicate

The chemical properties of berylThe chemical properties of beryl

Beryl is a beryllium aluminum silicate BeBeryl is a beryllium aluminum silicate Be33AlAl22(Si(Si66OO1818) )

Composition:Composition:

The vertical hexagonal channels, which are normally vacant, can be The vertical hexagonal channels, which are normally vacant, can be occupied by alkali elements such as Li, Na, and Rb or neutral occupied by alkali elements such as Li, Na, and Rb or neutral molecules such as Hmolecules such as H22O or COO or CO22..

Similar but rare species include Euclase [BeAl(SiOSimilar but rare species include Euclase [BeAl(SiO44)(OH)] and )(OH)] and

gadolinite [YFegadolinite [YFe2+2+BeBe22(SiO(SiO44))22OO22] ]

BeO: 14.0%BeO: 14.0%AlAl22OO33: 19.0%: 19.0%SiOSiO22: 67.0%: 67.0%

This image shows the hexagonal This image shows the hexagonal structure along the c-axis of berylstructure along the c-axis of beryl

Silica tetrahedra (upper layer)Silica tetrahedra (upper layer)

Beryllium tetrahedraBeryllium tetrahedra

Silica tetrahedra (lower layer)Silica tetrahedra (lower layer)

Aluminum polyhedronAluminum polyhedron

The crystallographic properties of berylThe crystallographic properties of beryl

Crystal system: hexagonalCrystal system: hexagonal

Point Group: 6/m 2/m 2/mPoint Group: 6/m 2/m 2/m

Space group: P6/mccSpace group: P6/mcc

Unit cell parameters:Unit cell parameters: a = 9.23 a = 9.23 ÅÅ

c

ba

c = 9.19c = 9.19ÅÅZ = 2Z = 2

Beryl tetrahedronBeryl tetrahedron

Aluminum polyhedronAluminum polyhedron

Silicon tetrahedronSilicon tetrahedron

Oxygen atomOxygen atom

The crystallographic properties of berylThe crystallographic properties of beryl

c

ba

Beryl tetrahedronBeryl tetrahedron

Aluminum polyhedronAluminum polyhedron

Silicon tetrahedronSilicon tetrahedron

Oxygen atomOxygen atom

Crystallographic data of berylCrystallographic data of beryl

Source: Morosin (1972)Source: Morosin (1972)

The optical properties of berylThe optical properties of beryl

Beryl is uniaxial negative (oblate indicatrix)Beryl is uniaxial negative (oblate indicatrix)

= 1.560 – 1.602= 1.560 – 1.602

= 1.557 – 1.599= 1.557 – 1.599

= 0.045 (3= 0.045 (3rdrd order interference colors) order interference colors)

Weak to distinct pleochroismWeak to distinct pleochroism

May be zonedMay be zoned

May be twinnedMay be twinned

The thermodynamic properties of berylThe thermodynamic properties of beryl

Open circles Open circles are for berylare for beryl

Closed circles Closed circles are for emeraldare for emerald

a axis

c axis

Both crystals exhibit a negative Both crystals exhibit a negative thermal expansion along the thermal expansion along the cc axis axis

Source: Morosin (1972)Source: Morosin (1972)

Occurrences of BerylOccurrences of Beryl

Igneous rocksIgneous rocks

Metamorphic rocksMetamorphic rocks

In granite, granite pegmatite, rarely in nepheline In granite, granite pegmatite, rarely in nepheline syenitesyenite

In low to high temperature hydrothermal veinsIn low to high temperature hydrothermal veins

Associated minerals include micas, quartz, euclase, calcite, Associated minerals include micas, quartz, euclase, calcite, tourmaline, lepidote, spodumene, cassiterite topaz, and feldsparstourmaline, lepidote, spodumene, cassiterite topaz, and feldspars

Locations on Earth:Locations on Earth: Colombia, Brazil, Madagascar, Zimbabwe, Pakistan, Colombia, Brazil, Madagascar, Zimbabwe, Pakistan, Afghanistan, Russia, United States (Ca, Co, Id, Ut, NC) Afghanistan, Russia, United States (Ca, Co, Id, Ut, NC)