CHEMISTRY INVESTIGATORY PROJECT

CHEMISTRY OF
GEMSTONES
AY - 2024-2025

Prepared by
Praanav Karthik M
Sukirthan k
Murugappan A
 INTRODUCTION
Gemstones have captivated human imagination
for centuries, prized for their beauty, rarity, and
symbolic significance. Beyond their aesthetic
appeal, gemstones possess fascinating chemical
and structural properties that determine their
unique characteristics. The chemistry of
gemstones is a captivating field that reveals the
intricate relationships between atomic
arrangements, chemical composition, and optical
properties.

Gemstones are naturally occurring minerals or

rocks that owe their color, hardness, and
brilliance to their chemical makeup. The diverse
array of gemstones, including diamonds, rubies,
emeralds, sapphires, and quartz, arise from
varying combinations of elements, crystal
structures, and impurities.
 KEY CONCEPTS OF
CHEMISTRY OF GEMSTONES
Chemical Composition

1. Elemental makeup: Gemstones are composed of various

elements (e.g., carbon, silicon, oxygen, aluminum, iron).
2. Molecular structure: Arrangement of atoms within the
gemstone.

Crystal Structure

1. Crystal lattice: Three-dimensional arrangement of atoms.

2. Unit cell: Smallest repeating unit of the crystal lattice.
3. Crystal system: Classification based on lattice symmetry
(e.g., cubic, hexagonal).

Chemical Bonding

1. Covalent bonds: Sharing electrons between atoms.

2. Ionic bonds: Electrostatic attraction between oppositely
charged ions.
3. Van der Waals forces: Weak intermolecular forces.
Impurities and Defects

1. Trace elements: Small amounts of elements affecting color,

clarity.
2. Inclusions: Internal features (e.g., veins, cavities).
3. Defects: Irregularities in crystal structure.

Optical Properties

1. Refraction: Bending of light.

2. Reflection: Light scattering.
3. Absorption: Light absorption by impurities.

Gemstone Classification

1. Mineral family: Grouping by chemical composition (e.g.,

quartz, feldspar).
2. Chemical groups: Classification by dominant elements (e.g.,
oxides, silicates).

Gemstone Properties

1. Hardness: Resistance to scratching.

2. Density: Mass per unit volume.
3. Cleavage: Tendency to break along crystal planes.
Some key chemical formulas
and composition of popular
gemstones:

1. Diamond: C (pure carbon)

2. Ruby: Al2O3 (aluminum oxide

with chromium impurities)

3. Emerald: Be3Al2Si6O18 (beryl

with chromium and vanadium)

4. Sapphire: Al2O3 (aluminum

oxide with iron and titanium)

5. Quartz: SiO2 (silicon dioxide)

Here's a comprehensive
note on the chemistry of
different types of
gemstones
 Diamonds

- Chemical formula: C (pure carbon)

- Crystal structure: Isometric (face-centered
cubic)
- Composition: 99.95% carbon, with impurities
like nitrogen, hydrogen
- Properties: Hardness (10), density (3.52
g/cm³), refractive index (2.42)
- Occurrence: Formed through high-pressure,
high-temperature processes
 Rubies and Sapphires
- Chemical formula: Al2O3 (aluminum oxide)
- Crystal structure: Hexagonal (corundum)
- Composition: Aluminum oxide with
chromium (ruby) or iron and titanium
(sapphire)
- Properties: Hardness (9), density (3.9-4.1
g/cm³), refractive index (1.76-1.82)
- Occurrence: Formed through metamorphic
processes
 Emeralds

- Chemical formula: Be3Al2Si6O18 (beryl)

- Crystal structure: Hexagonal
- Composition: Beryllium, aluminum, silicon,
oxygen, with chromium and vanadium
impurities
- Properties: Hardness (7.5-8), density (2.67-
2.78 g/cm³), refractive index (1.56-1.60)
- Occurrence: Formed through hydrothermal
processes
 Quartz
- Chemical formula: SiO2 (silicon dioxide)
- Crystal structure: Trigonal
- Composition: Silicon, oxygen, with
impurities like aluminum, iron
- Properties: Hardness (7), density (2.65
g/cm³), refractive index (1.54-1.55)
- Occurrence: Formed through igneous,
sedimentary, and metamorphic processes
 Opals
- Chemical formula: SiO2·nH2O (silicon
dioxide with water)
- Crystal structure: Amorphous
- Composition: Silicon, oxygen, water, with
impurities like aluminum, iron
- Properties: Hardness (5.5-6.5), density (1.9-
2.2 g/cm³), refractive index (1.44-1.47)
- Occurrence: Formed through sedimentary
processes
 Turquoise
- Chemical formula: CuAl6(PO4)6(OH)8·4H2O
(copper aluminum phosphate hydroxide)
- Crystal structure: Triclinic
- Composition: Copper, aluminum,
phosphorus, oxygen, hydrogen
- Properties: Hardness (5-6), density (2.9-3.2
g/cm³), refractive index (1.61-1.65)
- Occurrence: Formed through hydrothermal
processes
 Different types of
gemstones

Gemstones are classified into several categories based

on their chemical composition, crystal structure, and
optical properties.

Here's a comprehensive list of different types of

gemstones:

Mineral Gemstones
1. Diamond (C)
2. Ruby (Al2O3)
3. Sapphire (Al2O3)
4. Emerald (Be3Al2Si6O18)
5. Quartz (SiO2)
6. Topaz (Al2SiO4(F,OH)2)
7. Garnet (X3Y2(SiO4)3)
8. Peridot (Mg2SiO4)
9. Opal (SiO2·nH2O)
10. Turquoise (CuAl6(PO4)6(OH)8·4H2O)
Organic Gemstones

1. Pearl (CaCO3)
2. Coral (CaCO3)
3. Amber (fossilized tree resin)
4. Jet (fossilized wood)
5. Ivory (animal teeth and tusks)

Rock Gemstones

1. Lapis lazuli (metamorphic rock)

2. Jade (metamorphic rock)
3. Malachite (copper carbonate mineral)
4. Onyx (banded chalcedony)
5. Sodalite (feldspathoid mineral)

Synthetic Gemstones
1. Lab-created diamonds
2. Synthetic rubies and sapphires
3. Synthetic emeralds
4. Synthetic quartz
5. Glass-filled rubies
 Chemical reactions in
chemistry of gem stone

Formation Reactions
1. Diamond formation: C (graphite) → C (diamond)
(high-pressure, high-temperature process)
2. Ruby formation:
Al2O3 (corundum) + Cr3+ → Al2O3:Cr (ruby)
3. Emerald formation:
Be3Al2Si6O18 (beryl) + Cr3+ + V3+ → Be₃Al₂Si₆O₁₈:Cr,V
(emerald)
4. Quartz formation: SiO2 (silica) → SiO2 (quartz)
(hydrothermal process)

Alteration Reactions

1. Weathering:
Feldspar (KAlSi3O8) → Kaolinite (Al2Si2O5(OH)4) + Quartz
(SiO2)
2. Metamorphism: Calcite (CaCO3) → Marble (CaCO3)
(high-pressure, high-temperature process)
3. Hydrothermal alteration: Quartz (SiO2) → Amethyst (SiO2)
(iron-rich fluid interaction)
 Treatment Reactions
1. Heat treatment: Quartz (SiO2) → Citrine (SiO2)
(high-temperature process)
2. Irradiation: Diamond (C) → Color-enhanced diamond (C)
(electron or neutron irradiation)
3. Dyeing:
Porous gemstones (e.g., jade, quartz) + dye → Colored gemstone
4. Bleaching: Pearls (CaCO3) + bleach → Whitened pearls

Chemical Etching Reactions

1. Acid etching:
Quartz (SiO2) + HF (hydrofluoric acid) → Etched quartz surface

Gemstone Synthesis Reactions

1. Verneuil process:
Al2O3 (corundum) + Cr3+ → Synthetic ruby
2. High-pressure high-temperature (HPHT) process:
C (graphite) → Synthetic diamond
3. Hydrothermal synthesis:
SiO2 (silica) → Synthetic quartz
Chemical properties that affect
the chemistry of gem stones

Physical Properties

1. Hardness (Mohs scale): Resistance to scratching.

2. Density: Mass per unit volume.
3. Refractive Index (RI): Speed of light through the
gemstone.
4. Crystal Structure: Arrangement of atoms.

Chemical Properties

1. Chemical Composition: Elemental makeup.

2. Valency: Number of electrons transferred or shared.
3. Electro negativity (EN): Ability to attract electrons.
4. Ionization Energy: Energy required to remove
electrons.
5. Solubility: Ability to dissolve in solutions.
Impurities and Defects

1. Trace elements: Small amounts of elements affecting

color, clarity.
2. Inclusions: Internal features (e.g., veins, cavities).
3. Defects: Irregularities in crystal structure.

Chemical Processes
1. Magmatic crystallization: Magma cooling and
solidification.
2. Metamorphic recrystallization: High-pressure, high-
temperature transformation.
3. Hydrothermal growth: Hot water-rich fluid interaction.
4. Weathering and erosion: Surface chemical reactions.

Analytical Techniques

1. X-Ray Fluorescence (XRF): Elemental analysis.

2. Infrared (IR) Spectroscopy: Molecular structure
analysis.
3. Raman Spectroscopy: Molecular structure
analysis.
4. Scanning Electron Microscopy (SEM): Surface
analysis
 How can gem stones be
preserved properly?

Proper preservation and care of gemstones involve

understanding their unique properties and
vulnerabilities.

Here are some tips to help preserve your

gemstones:

General Care
1. Store gemstones separately to prevent scratching.
2. Avoid exposure to direct sunlight, heat, or radiation.
3. Keep gemstones away from chemicals, cleaning
products, and perfumes.
4. Avoid wearing gemstones during physical activities or
sports.
5. Clean gemstones regularly with mild soap and water.

Cleaning Methods
1. Soft cloth and mild soap for most gemstones.
2. Ultrasonic cleaner for diamonds, rubies, and
sapphires.
3. Avoid steam cleaning for emeralds, pearls, and opals.
4. Avoid harsh chemicals or abrasive materials.
Specific Care for Common Gemstones
1. Diamond: Avoid exposure to high heat, chemicals, or
abrasive materials.
2. Ruby/Sapphire: Avoid exposure to high heat,
chemicals, or intense light.
3. Emerald: Avoid exposure to heat, chemicals, or
sudden temperature changes.
4. Pearl: Avoid exposure to chemicals, heat, or direct
sunlight.
5. Opal: Avoid exposure to heat, dryness, or chemicals.

Preventive Measures
1. Regular inspections for damage or wear.
2. Avoid exposing gemstones to extreme
temperatures.
3. Use gemstone-setting techniques that minimize
damage.
4. Consider insurance coverage.

Resources

1. Gemological Institute of America (GIA)

2. International Colored Gemstone Association (ICA)
3. American Gem Trade Association (AGTA)
4. National Association of Jewelry Appraisers (NAJA)
 Conclusion

In conclusion, the chemistry of gemstones reveals the

intricate relationships between atomic arrangements,
chemical composition, and optical properties. Through this
project, we explored the chemical properties, formation
processes, and preservation techniques of various gemstones.
Our findings highlight the significance of understanding
gemstone chemistry in authentication, valuation, and care.

The diversity of gemstone chemistry, from diamond's pure

carbon structure to emerald's complex silicate composition,
demonstrates the remarkable range of chemical possibilities
in nature. Moreover, human interventions, such as heat
treatment and synthesis, further expand the chemical
spectrum of gemstones.

This project underscores the importance of interdisciplinary

approaches, combining geology, materials science, and
chemistry to appreciate the beauty and rarity of gemstones.
As our knowledge of gemstone chemistry evolves, so does our
ability to preserve, authenticate, and cherish these natural
wonders.

Ultimately, the chemistry of gemstones reminds us of the

awe-inspiring complexity and beauty of the natural world.
 Bibliography

https://chemart.rice.edu
https://www.geologyin.com
https://edu.rsc.org

THANK YOU