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Questions and Answers
Equilibrium crystallization occurs in an open system where crystals do not remain in contact with the melt.
Equilibrium crystallization occurs in an open system where crystals do not remain in contact with the melt.
False
The composition of the liquid at the solidus line indicates the highest temperature at which liquid can exist.
The composition of the liquid at the solidus line indicates the highest temperature at which liquid can exist.
False
The liquidus line specifies the composition of liquid co-existing with a solid at a given temperature.
The liquidus line specifies the composition of liquid co-existing with a solid at a given temperature.
True
In fractional crystallization, what you start with is what you end up with.
In fractional crystallization, what you start with is what you end up with.
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The composition of the first crystal formed can be determined at a specific temperature during cooling.
The composition of the first crystal formed can be determined at a specific temperature during cooling.
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The Lever Rule is used to determine the proportions of liquid and solid phases in a system at equilibrium.
The Lever Rule is used to determine the proportions of liquid and solid phases in a system at equilibrium.
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Filtering is one of the processes that can lead to non-equilibrium crystallization.
Filtering is one of the processes that can lead to non-equilibrium crystallization.
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Crystals formed during crystallization generally always have the same density as the liquid they originated from.
Crystals formed during crystallization generally always have the same density as the liquid they originated from.
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The lever rule can be applied to determine the phase proportions of a system in equilibrium crystallization.
The lever rule can be applied to determine the phase proportions of a system in equilibrium crystallization.
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At 1800 °C, the only phase present in the system is solid.
At 1800 °C, the only phase present in the system is solid.
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As the temperature decreases from 1625 °C to 1410 °C, the composition of the liquid phase becomes less Fe rich.
As the temperature decreases from 1625 °C to 1410 °C, the composition of the liquid phase becomes less Fe rich.
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The final composition of the last bit of melt occurs at a temperature below 1410 °C.
The final composition of the last bit of melt occurs at a temperature below 1410 °C.
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At 1450 °C, the melt composition remains constant while the solid composition evolves.
At 1450 °C, the melt composition remains constant while the solid composition evolves.
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During the evolution from 1800 °C to 1625 °C, the solid composition evolves along the solidus.
During the evolution from 1800 °C to 1625 °C, the solid composition evolves along the solidus.
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The first crystals form at or above 1800 °C.
The first crystals form at or above 1800 °C.
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The proportion of melt decreases as temperature decreases during cooling.
The proportion of melt decreases as temperature decreases during cooling.
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Fractional crystallization occurs in a closed box system.
Fractional crystallization occurs in a closed box system.
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At 1500ºC, the composition of olivine crystals is consistent with the composition of the melt.
At 1500ºC, the composition of olivine crystals is consistent with the composition of the melt.
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The lever rule can be applied at 1500ºC to understand the phase proportions in the system.
The lever rule can be applied at 1500ºC to understand the phase proportions in the system.
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Once all solid is formed, the temperature remains constant regardless of the composition of the final solid.
Once all solid is formed, the temperature remains constant regardless of the composition of the final solid.
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In equilibrium crystallization, the liquid can evolve further along the liquidus than the composition of the co-existing solid.
In equilibrium crystallization, the liquid can evolve further along the liquidus than the composition of the co-existing solid.
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The first solid formed in a crystallization process has a temperature that is lower than that of the starting liquid.
The first solid formed in a crystallization process has a temperature that is lower than that of the starting liquid.
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The composition of the final solid is independent of the composition of the last bit of melt.
The composition of the final solid is independent of the composition of the last bit of melt.
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In fractional crystallization, the solid is removed from the system, which can affect the liquid's composition.
In fractional crystallization, the solid is removed from the system, which can affect the liquid's composition.
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Study Notes
Olivine
- Olivine is a primary igneous mineral found in mafic and ultramafic rocks like dunite, gabbro, peridotite, and basalt.
- Calcium-rich varieties are also found in metamorphic rocks.
- Solid solution phase diagrams are important in understanding olivine.
Structural Formula
- The structural formula of olivine is (Mg, Fe)₂SiO₄.
- This formula indicates that olivine can contain both magnesium (Mg) and iron (Fe) ions in its crystal structure.
- These elements replace each other in the structure, forming a solid solution.
- The silica (SiO₄) tetrahedra are arranged in a specific way in the structure.
Ca-Fe-Mg Ternary Diagram
- The Ca-Fe-Mg ternary diagram displays the chemical composition of olivine.
- The Mg–Fe ratio significantly impacts the physical properties of olivine, including density and crystallization temperature.
- The Ca-Mg and Fe-Mg end members are displayed.
Olivine: Structure
- Olivine is an example of an independent (or isolated) tetrahedral silicate, also called an island silicate or nesosilicate.
- The silicate tetrahedra are not connected to each other.
- The number of bridging oxygens for silicate tetrahedrons is zero.
- Olivine's structure features two different cation sites (A and B spots) in the crystal structure.
Phase Diagrams
- Phase diagrams are models for natural environments, based on lab studies.
- They help predict and interpret environmental mineral formation conditions (P-T).
- They also help determine the processes involved in the formation of these minerals.
Additional Notes
- Final group project assignment is available on LEAN.
- A lab session is scheduled for November 19/20. Work on the map beforehand.
- A preliminary report is required.
- There will be a quick introductory session regarding final assignments and expectations for presentations the following week.
- Bancroft presentations are scheduled for November 26/27 and attendance is mandatory.
- Midterm information appears on Learn. The structure of the midterm is similar to the previous year's exam.
- A midterm booking link is available on Learn for review.
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Description
Explore the fascinating world of olivine, a key igneous mineral found in various rocks such as dunite and basalt. This quiz covers its structural formula, its presence in metamorphic rocks, and the significance of solid solution phase diagrams. Test your knowledge on olivine's composition and the Ca-Fe-Mg ternary diagram.
