1. Beryl Beryl Aqua marine Emerald Goshenite Heliodor Morganite

2. Emerald: green variety The varieties of beryl Beryl: golden or red variety Morganite: pink variety Aquamarine: blue variety Heliodor: greenish-yellow variety Goshenite: colourless variety Interesting history: - Emeralds were mined in ancient Egypt 4000 years ago - 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 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 Group: beryl is a cyclosilicate

4. The chemical properties of beryl Beryl is a beryllium aluminum silicate Be 3 Al 2 (Si 6 O 18 ) Composition: 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 H 2 O or CO 2. Similar but rare species include Euclase [BeAl(SiO 4 )(OH)] and gadolinite [YFe 2+ Be 2 (SiO 4 ) 2 O 2 ] BeO: 14.0% Al 2 O 3 : 19.0% SiO 2 : 67.0% This image shows the hexagonal structure along the c-axis of beryl Silica tetrahedra (upper layer) Beryllium tetrahedra Silica tetrahedra (lower layer) Aluminum polyhedron

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

6. The crystallographic properties of beryl c b a 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 (3 rd order interference colors) Weak to distinct pleochroism May be zoned May be twinned

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

10. Occurrences of Beryl Igneous rocks Metamorphic rocks 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)