Comparison of Emeralds from the Chitral District, Pakistan, with other Pakistani and Afghan Emeralds

Comparison of Emeralds from the Chitral District, Pakistan, with other Pakistani and Afghan Emeralds" by Hanser et al. (2023), suitable for gemology students:

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🔷 Origin and Location

• Emerald Deposit: Chitral District, north-western Pakistan (discovered in 2021)

• Geological Zone: Outside the traditional “Emerald Belt” (Indus Suture Zone)

• Host Rocks: Quartz- and mica-rich metapelites of the Arkari Formation, intruded by pegmatitic leucogranite

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🪨 Rock Types and Formation

• Chitral emeralds form in schist-hosted environments

• Hosted in quartz- and mica-rich metamorphic rocks

• Similar to emeralds in Afghanistan's Panjshir and Swat (Pakistan), but geochemically distinct

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🎨 Color and Diaphaneity

• Colors: Light green to dark green

• Transparency: Mostly transparent; higher-quality than earlier samples

• Notable: Deeper-colored samples show potential for gem trade

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🔍 Inclusions

• Chitral Inclusions:

  • Two-phase inclusions (gas + liquid)

  • Hollow growth tubes (some with yellowish precipitates)

  • Surface-reaching inclusions: quartz, plagioclase (andesine/oligoclase), K-feldspar, phlogopite (main dark mica), rare muscovite

• No three-phase inclusions, which is key to distinguishing from Panjshir, Swat, and Laghman emeralds

• Laghman: Biotite and three-phase inclusions

• Swat: Black opaque minerals (spinel, pyrite), talc, carbonate, and mica

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🔬 Optical & Physical Properties

Property	Chitral Emeralds
Refractive Index	1.580–1.590
Birefringence	0.008–0.009
SG	2.71–2.74
UV-Vis-NIR	Strong Fe²⁺ absorption (~830 nm)
Raman Spectra	Strong Type II H₂O peaks

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🧪 Chemical Composition (Major/Trace Elements)

By EPMA (Oxides, wt.%):

• SiO₂: ~63.6–64.4%

• Al₂O₃: ~15.3–16.1%

• FeO: ~0.45–0.63%

• MgO: ~1.6–1.9%

• Na₂O: ~1.5%

• BeO: Fixed ~13.6%

By LA-ICP-MS (ppm):

• High in:

  • Li: 938–1359 ppm (significantly higher than Swat, Panjshir, Laghman)

  • Cs: Up to 5782 ppm

  • Na: ~11,000–12,000 ppm

  • Mg: ~9,000–11,000 ppm

• Low in:

  • Mn: ~15–26 ppm

  • Ti: ~11–18 ppm

  • Zn: ~13–18 ppm

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💡 Cause of Color

• Chromophores: Chromium (Cr), Vanadium (V), and Iron (Fe)

• Chitral emeralds show:

  • Fe²⁺ dominant (responsible for bluish-green tone)

  • Moderate Cr and V contents

• Fe₂⁺ feature in UV-Vis (~830 nm) is stronger than Cr³⁺ and V³⁺, indicating schist-hosted genesis

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🧬 Elements (in ppm)

Element	Range	Characteristic
Li	938–1359	High – diagnostic for Chitral
Cs	1151–5782	High – separates from Swat
Cr	514–1197	Color contributor
V	222–391	Color contributor
Na	~11,000–12,000	Higher than Khaltaro
Fe	~3413–4164	Bluish-green tint source

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🔎 Diagnostic Features for Origin Determination

Property	Chitral vs Others
Inclusions	No three-phase; phlogopite-rich
Fe²⁺ Absorption	Stronger than Cr³⁺ & V³⁺
Li & Cs Levels	Significantly higher
Water Type (Raman)	Dominant Type II H₂O peaks
Growth Features	Weak zoning; no sawtooth structures

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📍 Summary for Students

• Chitral emeralds are schist-hosted, Fe²⁺-rich, and alkali-rich

• No three-phase inclusions (unlike Panjshir or Swat)

• High levels of Li and Cs make them chemically distinct

• Excellent for origin studies due to inclusion types, spectroscopic patterns, and chemical profiles

• Increasing mining activity in Chitral makes identification increasingly important in gem markets

Origin of Negative Crystals in Gemstones

What Are Negative Crystals in Gemstones?

Negative crystals are tiny, hollow shapes that form inside gemstones. These shapes look like small crystals and can be filled with liquids, gases, or other materials. Scientists have studied these crystals to understand how they form.

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How Do Negative Crystals Form?

Negative crystals can form in two main ways:

1. Healing Cracks:

   • When a gemstone gets a crack, it may come into contact with water or other liquids. Over time, the crack begins to heal, and tiny hollow shapes form. These are called secondary negative crystals.
   • Scientists have observed this process by heating synthetic rubies with cracks. The heat helps the healing process, forming these small, hollow crystals.

2. During Growth:

   • Sometimes, negative crystals form as the gemstone itself is growing. These are called primary negative crystals. They usually appear alone and are larger than secondary ones.

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Different Types of Negative Crystals

• In Synthetic Gemstones: Scientists found that heating synthetic rubies creates air-filled channels and hollow shapes that eventually turn into crystals.
• In Natural Gemstones: For example, spinels and peridots may have negative crystals. In peridots, the hollow shapes often look like bubbles but have crystal-like surfaces.

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Why Are They Important?

Negative crystals help gemologists (experts who study gemstones) understand how the gemstone was formed or if it has been treated. They are also useful in identifying whether a gem is natural or synthetic.

Special Cases • Peridot: Contains rounded gas bubbles that, under reflected light, exhibit crystal faces, confirming them as negative crystals formed during growth. Negative crystals provide valuable insights into the growth and healing processes of gemstones. They are important for both gemological studies and aesthetic appreciation.

Corundum MCQs

Corundum MCQ Quiz (50 Questions)

Sodalite from Myanmar vs. Afghanistan: A Complete Comparison

Sodalite is a fascinating gemstone known for its vibrant blue hues and unique tenebrescence, the ability to change color under UV light. In recent years, high-quality sodalite (also called hackmanite) has been sourced from Myanmar and Afghanistan. If you are a gem collector, jeweler, or enthusiast looking to understand the differences between these two sources, this comprehensive comparison will help you make an informed choice.

1. General Characteristics

• Tenebrescence: Both Myanmar and Afghan sodalite exhibit tenebrescence, allowing them to change color when exposed to UV light.

• Transparency: Afghan sodalite is typically more transparent, whereas Burmese sodalite tends to have more inclusions.

2. Transparency & Clarity

• Afghan Sodalite: Cleaner, with fewer inclusions and higher transparency.

• Burmese Sodalite: More included, often with visible fractures and foreign material.

3. Color and Tenebrescence

• Burmese Sodalite: Usually has a deeper, richer purple or violet color.

• Afghan Sodalite: Ranges from very light violet to medium purple.

• Tenebrescence: Afghan sodalite generally has a stronger tenebrescence effect than Burmese sodalite.

4. UV Fluorescence and Phosphorescence

• Afghan Sodalite: Strong yellow to orange fluorescence under long-wave UV, moderate to strong white fluorescence under short-wave UV.

• Burmese Sodalite: Weaker fluorescence, typically greenish-yellow in fractures.

• Phosphorescence: Afghan sodalite shows stronger phosphorescence than Burmese sodalite.

5. Refractive Index & Specific Gravity

• Afghan Sodalite: Refractive index of 1.45 - 1.48.

• Burmese Sodalite: Refractive index of 1.47 - 1.48.

• Specific Gravity: Burmese sodalite sometimes has a higher SG (up to 2.44) due to the presence of nepheline inclusions.

6. Spectroscopy & Chemistry

• Both types contain traces of sulfur, which contribute to tenebrescence.

• Afghan sodalite exhibits additional spectral features in UV-Vis-NIR spectra, such as peaks at 410-412 nm, 277 nm, and 313 nm, which are not found in Burmese sodalite.

7. Treatment

• Afghan Sodalite: Often oiled to enhance clarity.

• Burmese Sodalite: May also undergo oiling, especially after cutting.

Conclusion: Which One Should You Choose?

• If you want a gemstone with strong tenebrescence, Afghan hackmanite is the better choice.

• If you prefer a deep, rich purple or violet color, Burmese sodalite is ideal.

• For higher transparency and fewer inclusions, Afghan sodalite is superior.

• If you appreciate UV fluorescence and phosphorescence, Afghan sodalite offers stronger effects.

Final Thoughts

Both Myanmar and Afghan sodalite have their own unique appeal. Whether you’re a gem enthusiast, collector, or jeweler, understanding these differences can help you make a more informed decision. For investment or aesthetic purposes, consider your preference for tenebrescence, clarity, and fluorescence when choosing between these two beautiful varieties of sodalite.

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• Title: Sodalite from Myanmar vs. Afghanistan – Differences, Color, & Value

• Meta Description: Discover the key differences between Burmese and Afghan sodalite, including color, tenebrescence, transparency, UV fluorescence, and treatment.

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Gemology MCQs Part 6

Test Your Knowledge in Gemology Part 6

1. A 2-carat fine-quality ruby is worth more than 10 rubies of the same color and quality, which have a total weight of 4 carats.

a) True
b) False

Correct Answer: a) True

2. One carat equals:

a) 1 gram
b) 1/10 of a gram
c) 1/5 of a gram
d) 1/2 of a gram

Correct Answer: c) 1/5 of a gram

3. A ten-pointer is a stone that weighs:

a) 10 carats
b) 1/10 of a carat
c) 10 facet junctions
d) 10 grams

Correct Answer: b) 1/10 of a carat

4. When comparing gem prices, you should compare their:

a) Per-carat cost
b) Overall size
c) Density
d) Facet count

Correct Answer: a) Per-carat cost

5. If a Tanzanite weighs 4 carats and costs $1600, what is its per-carat price?

a) $200
b) $400
c) $800
d) $1600

Correct Answer: b) $400

6. What is the cost of a 0.25-carat ruby that sells for $400 per carat?

a) $25
b) $50
c) $100
d) $400

Correct Answer: c) $100

7. A 1-carat round emerald would typically cost less than a 1-carat emerald-cut emerald, all other factors being equal.

a) True
b) False

Correct Answer: a) False

8. All step cuts are emerald cuts.

a) True
b) False

Correct Answer: b) False

9. Which cut is most commonly used for rubies and sapphires?

a) Emerald cut
b) Mixed cut
c) Brilliant cut
d) Cabochon cut

Correct Answer: b) Mixed cut

10. The large top facet of a stone is called?

a) Pavilion
b) Crown
c) Table
d) Girdle

Correct Answer: c) Table

11. The narrow rim around the circumference of a stone is called the:

a) Pavilion
b) Crown
c) Table
d) Girdle

Correct Answer: d) Girdle

Gemology MCQs Part-5

Test Your Knowledge in Gemology Part-5

1. Fancy cut diamonds are those with shapes that are not standard round brilliant cut.

True False

2. Alluvial deposits are those in which the gems are mined from soft rocks.

True False

3. Which gemstone has a greater range of colors?

Corundum Beryl Tourmaline

4. Rubies are sometimes oiled to help mask fractures.

True False

5. Ruby can be found in different colours other than red.

True False

6. The hardness on the Moh's Scale of spinel is 8.

True False

7. Emerald and aquamarine have the same chemical composition.

True False

8. Padparadscha sapphire is also called fancy sapphire.

True False

9. Emeralds are occasionally treated with colored fillers to make them look greener.

True False

10. Pink topaz occurs in Pakistan.

True False

Gemology MCQs Part-4

Test Your Knowledge in Gemology Part-4

1. The refractive index of diamond is 2.40.

True False

2. Cleavage in gemstones results from directional weakness in atomic bonding.

True False

3. Dark field illumination is helpful in observing asterism effect in gemstones.

True False

4. A gem material that contains absolutely no transition elements will usually be colorless.

True False

5. The Chelsea filter test is especially useful for detecting chromium.

True False

6. The most highly prized of all sapphire colors is blue sapphire from Kashmir, India.

True False

7. As emeralds get lighter in color, their value decreases.

True False

8. Padparadscha sapphire is a variety of pinkish orange sapphire.

True False

9. In the GIA color grade scale, truly colorless diamonds receive a grade of “D.”

True False

10. Lasering as an enhancement process is used to improve the appearance of diamonds.

True False