2016/17 Undergraduate Module Catalogue

SOEE2580 Gemstones

10 creditsClass Size: 60

Module manager: Dr Dan Morgan
Email: d.j.morgan@leeds.ac.uk

Taught: Semester 2 (Jan to Jun) View Timetable

Year running 2016/17

Pre-requisite qualifications

As listed (or eqivalent for incoming study abroad students)

Pre-requisites

SOEE1570	Geology 1
SOEE1580	Geology 2

This module is not approved as a discovery module

Module summary

Have you ever wondered where gemstones come from? What makes them valuable? Why they have the colours that they do, and how we identify them? How are gemstones used around us in technological materials, and how are they grown in the lab? This module looks at the different gemstone families (diamond, corundums (ruby and sapphire) and beryls (emeralds)), as well as the semi-precious gemstones. The module examines all of the above in a mineralogical and geological context as well as the ethics of gemstone exploration and its effects. The module develops concepts introduced in Mineralogy and their application to gemstones as geological materials. Learn the role of the gemmologist and how to use gemmological instruments, and have the opportunity to examine genuine gemstones.

Objectives

To introduce students to the different varieties of precious and semi-precious gemstones, via consideration of their mineralogy, crystallography, origins and extraction.

Learning outcomes
The module will introduce the students to advanced topics in mineralogy through the engaging interface of gemstones. Students will discover the main classes of precious and semi-precious gems, their origins and extraction, understand the origins of colour in gemstones and crystals, and understand the techniques by which gemstones can be identified (X-ray diffraction, Spectrographs). The module is intended to have broad appeal but to drive relatively complex concepts in “hard” mineralogy using gemstones as the testbed. Example outcomes:

- The origin of colour in gemstones – valence band electrons, colour centres, quantum effects and diffraction (of light).
- Growing artificial gemstones – methods used include Verneuil, Czochranski, and Hydrothermal cells.
- Diamond minerals – occurrence, use (industrial and domestic), igneous and metamorphic parageneses, economics and ethics
- Corundum minerals – occurrence, use (industrial and domestic), igneous and metamorphic parageneses, economics and ethics
- Beryl minerals (inc. Emeralds) – occurrence, igneous and metamorphic parageneses, economics and ethics
- Gemstone treatments – processing of gems to enhance colour and clarity, relationship to concepts of phase petrology studied in mineralogy; exsolution, inclusions and colour chemistry.
- Schiller in minerals, origins and explanation, mechanics of light diffraction, relationship to feldspar structure and chemistry
- Methods to identify crystals, both destructive and non-destructive. Case study for development: X-ray diffraction, in particular the use of powder diffraction
- More gemstone treatments: irradiation, ionic implantation, fillers, triplets and oils
- Predicting gemstone behaviour and properties based upon understanding of its phase diagram.
- Exploration strategies for locating deposits: diamond example
- Gemstone provenancing using trace chemical (destructive) and optical (non-destructive) means

The module will also introduce concepts in the ethics of gemstone extraction and processing as part of the enrichment value of the course.

Skills outcomes
The module develops skills in crystallography, mineralogy and practical data gathering and analysis, such as optical spectrometry and X-Ray diffraction.

Syllabus

Lecture 1: What is a gemstone?
Practical: Semi-precious stones, their characteristics and properties. Revision of basic hand specimen descriptions, introduction to various phenomena that will come back later.

Lecture 2: The origins of colour in gemstones
Practical: The origins of the colours of various gemstones seen in practical 1.
Tutorials start this week

Lecture 3: Diamonds: origin, properties, mining and occurrence
Practical: Kimberlites and xenoliths, prospecting for diamond

Lecture 4: The corundum group: rubies and sapphires, their origin, properties, mining and occurrence
Practical: Exsolution in gemstones, exsolution as a thermochronometer.

Lecture 5: Beryls – the Emerald group, occurrence, origins, and example mines, ethics of exploitation: Colombia.
Practical: Crystal growth, inclusions and flaws; their origin and formation.

Lecture 6: Gemstone treatments
Practical: Heat treatment of minerals, effect on exsolution and colour (follows on from practical 4)

Lecture 7: Schiller and diffractive minerals
Practical: Why is Schiller usually blue? Diffraction gratings, crystal growth and annealing

Lecture 8: Identifying minerals and gemstones.
Practical: Refresher on mineral lattices and powder diffraction patterns. Classification of minerals from powder diffractograms.

Lecture 9: Manufactured gemstones and gem cutting
Practical: Gemstone provenancing. Identifying a gemstone from physical properties (X-ray properties, diffraction data, Colours, Fluorescence, Spectra, Crystallography).

Lecture 10: Artificial gemstones: growing corundums, beryls, diamonds and cubic zirconia
Practical: The materials science of crystal growth in the laboratory, how to overcome natural kinetics.

Lecture 11: The economics and ethics of gemstones: a historical perspective of the DeBeers corporation, conflict and blood gems.
Practical: Tracing the illicit trade in diamonds - where did mystery diamonds X, Y and Z come from?

Teaching methods

Delivery type	Number	Length hours	Student hours
Lecture	11	1.00	11.00
Practical	11	2.00	22.00
Tutorial	1	2.00	2.00
Independent online learning hours			20.00
Private study hours			45.00
Total Contact hours			35.00
Total hours (100hr per 10 credits)			100.00

Private study

There will be weekly reading assignments and also online exercises and materials to review. The coursework assessment (50%) is a short essay (1200 words) researched on a specific type of gemstone from beyond the main course, giving its composition, characteristics, economic value, origins and mode of formation, production sites and methods, ethical implications (as applicable) for production, and, if applicable, industrial uses.

Opportunities for Formative Feedback

Practical classes give a weekly contact point for feedback and assessment of progress.

Methods of assessment

Coursework

Assessment type	Notes	% of formal assessment
Essay	1,200 word researched essay on a named gemstone outside the main syllabus	50.00
Total percentage (Assessment Coursework)		50.00

Normally resits will be assessed by the same methodology as the first attempt, unless otherwise stated

Exams

Exam type	Exam duration	% of formal assessment
Standard exam (closed essays, MCQs etc)	1 hr 00 mins	50.00
Total percentage (Assessment Exams)		50.00

The exam would consist of a short answer section (20 minutes, compulsory) and a short essay from a selection of three (40 minutes).

Reading list

The reading list is available from the Library website

Last updated: 17/08/2016

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