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Beryl

Beryl. Aqua marine. Heliodor. Morganite. Emerald. Goshenite. Beryl. The varieties of beryl. Beryl: golden or red variety. Emerald: green variety. Aquamarine: blue variety. Morganite: pink variety . Heliodor: greenish-yellow variety. Goshenite: colourless variety.

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Beryl

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  1. Beryl Aqua marine Heliodor Morganite Emerald Goshenite Beryl

  2. The varieties of beryl Beryl: golden or red variety Emerald: green variety Aquamarine: blue variety Morganite: pink variety Heliodor: greenish-yellow variety Goshenite: colourless variety - Emeralds were mined in ancient Egypt 4000 years ago Interesting history: - In the 1600’s, high quality emerald reached Europe. - The Spaniards seized the emeralds from the Pre-Colombian people. - Mining in Colombia is still going on today, and often associated with criminal activities.

  3. The physical properties of beryl Group: beryl is a cyclosilicate Luster: vitreous, transparent to translucent Cleavage: imperfect in one direction, conchoidal fracture Hardness: 7.5 - 8 Specific gravity: 2.6 – 2.9 on average Crystal habit: hexagonal prism with pincoid termination

  4. The chemical properties of beryl Beryl is a beryllium aluminum silicate Be3Al2(Si6O18) BeO: 14.0% Composition: Al2O3: 19.0% SiO2: 67.0% The vertical hexagonal channels, which are normally vacant, can be occupied by alkali elements such as Li, Na, and Rb or neutral molecules such as H2O or CO2. This image shows the hexagonal structure along the c-axis of beryl Silica tetrahedra (upper layer) Silica tetrahedra (lower layer) Beryllium tetrahedra Aluminum polyhedron Similar but rare species include Euclase [BeAl(SiO4)(OH)] and gadolinite [YFe2+Be2(SiO4)2O2]

  5. c a b The crystallographic properties of beryl Crystal system: hexagonal Point Group: 6/m 2/m 2/m Unit cell parameters: a = 9.23 Å c = 9.19Å Z = 2 Space group: P6/mcc Beryl tetrahedron Aluminum polyhedron Silicon tetrahedron Oxygen atom

  6. b a c The crystallographic properties of beryl Beryl tetrahedron Aluminum polyhedron Silicon tetrahedron Oxygen atom

  7. Crystallographic data of beryl Source: Morosin (1972)

  8. The optical properties of beryl Beryl is uniaxial negative (oblate indicatrix)  = 1.560 – 1.602  = 1.557 – 1.599  = 0.045 (3rd order interference colors) Weak to distinct pleochroism May be zoned May be twinned

  9. a axis c axis The thermodynamic properties of beryl Open circles are for beryl Closed circles are for emerald Both crystals exhibit a negative thermal expansion along the c axis Source: Morosin (1972)

  10. Igneous rocks Metamorphic rocks Occurrences of Beryl In granite, granite pegmatite, rarely in nepheline syenite In low to high temperature hydrothermal veins Associated minerals include micas, quartz, euclase, calcite, tourmaline, lepidote, spodumene, cassiterite topaz, and feldspars Locations on Earth: Colombia, Brazil, Madagascar, Zimbabwe, Pakistan, Afghanistan, Russia, United States (Ca, Co, Id, Ut, NC)

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