Aquamarine – Crystal Wiki
The shimmering sea-blue gemstone from the beryl family – prized for its purity and clarity
var. Aquamarine (Beryl group, Be₃Al₂Si₆O₁₈)
Properties & Characteristics
🔬 Scientific Data
- Chemical Formula
- Be₃Al₂Si₆O₁₈ (Beryllium Aluminum Silicate)
- Crystal System
- Hexagonal
- Mohs Hardness
- 7.5–8
- Density
- 2.68–2.74 g/cm³
- Refractive Index
- 1.577–1.583
💎 Physical Properties
- Color
- Light blue to deep blue, often with a slight greenish tint
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Streak
- White
- Cleavage
- Imperfect in one direction (perpendicular to the c-axis)
- Fracture
- Conchoidal to uneven
🌍 Occurrence
- Main Localities
- Pakistan, Brazil, Madagascar, Nigeria, Mozambique
- Important Deposits
- Gilgit-Baltistan (PK), Minas Gerais (BR), Ambatovita (MG)
✨ Uses & Value
- Uses
- Jewelry (faceting), collector's items, healing stones
- Value Range
- Faceted aquamarines often range from approx. €30–€400 per ct, with particularly intense qualities significantly higher; large rough crystals and collector's specimens are typically traded in the range of approx. €80–€2,000+ per piece.
What is Aquamarine?
Aquamarine is the blue variety of the mineral beryl – thus belonging to the same mineral family as emerald. Its name is derived from the Latin "aqua marina," meaning "seawater." The name perfectly describes its clear, shimmering sea-blue color.
Formation
Aquamarine crystallizes in pegmatites – coarse-grained rocks that form in the final phase of magma cooling. The crystals grow slowly in cavities and fissures and can reach considerable sizes. Its blue color is due to traces of iron (Fe²⁺) in the crystal structure.
Origin & Localities
The finest specimens come from Pakistan (Gilgit-Baltistan, Skardu), characterized by their clarity and intense blue color. Brazil (Minas Gerais) is the largest producer by volume. Other important localities include Madagascar, Nigeria, Mozambique, and Afghanistan. Pakistani aquamarines command the highest prices due to their intense color.
Special Features
- Size: Aquamarine often forms large, clean crystals. The largest known aquamarine (Dom Pedro, Brazil) weighed over 45 kg in its rough state.
- Pleochroism: Aquamarines exhibit slightly different shades of blue depending on the viewing angle – a sign of authenticity.
- Heating: Many aquamarines are gently heated (approx. 400 °C) to remove greenish tones and achieve a pure blue. This is a permanent, generally accepted treatment.
Quality Characteristics
The ideal aquamarine shows a rich, pure blue without visible inclusions. The deeper and more saturated the blue, the more valuable it is – the finest quality is known as "Santa Maria" blue (named after the Brazilian mine). Large, eye-clean stones with intense color are among the most sought-after gemstones on the market.
Frequently Asked Questions
What is the difference between aquamarine and blue topaz?
Although both stones appear blue, they differ fundamentally: Aquamarine belongs to the beryl family (like emerald) and has a natural, gentle blue tint due to iron. Blue topaz is almost always irradiated and heated to achieve its intense color. Aquamarine is also softer (7.5–8 vs. 8 Mohs) and exhibits characteristic pleochroism.
Why are Pakistani aquamarines so valuable?
Aquamarines from Pakistan (especially Gilgit-Baltistan and Skardu) exhibit an exceptionally intense, deep blue with high clarity. The extreme mining conditions in the Karakoram Mountains at over 4,000 meters altitude make transportation difficult and quantities limited, further driving up the price.
Is it normal for aquamarines to be heated?
Yes, heating aquamarine is a generally accepted and widespread treatment. Greenish color components are removed at approx. 400 °C to achieve a pure blue. The treatment is permanent, stable, and customary in the gemstone trade.
Detailed Information
Properties & Composition
Chemical Formula: Be₃Al₂Si₆O₁₈ (Beryllium Aluminum Silicate)
Crystal System: Hexagonal
Mohs Hardness: 7.5–8
Density: 2.68–2.74 g/cm³
Cleavage: Imperfect in one direction (perpendicular to the c-axis)
Fracture: Conchoidal to uneven
Luster: Vitreous
Transparency: Transparent to translucent
Streak: White
Refractive Index: 1.577–1.583
The blue color of aquamarine is caused by divalent iron ions (Fe²⁺) in the crystal structure. Greenish tones, often present in the rough state, are caused by trivalent iron ions (Fe³⁺) and can be removed by gentle heating.
Localities & Origin
Pakistan (Gilgit-Baltistan, Skardu): The finest and most valuable aquamarines worldwide. Intense blue coloration with high clarity. Mined under extreme conditions in the Karakoram Mountains at over 4,000 m altitude.
Brazil (Minas Gerais): Largest producer by volume. The famous "Santa Maria" quality comes from the mine of the same name. The legendary Dom Pedro Aquamarine (45 kg rough) was found here.
Madagascar: Supplies aquamarines of excellent quality with a rich blue. The deposits in Ambatovita and Antsirabe are known for large, clean crystals.
Nigeria: Relatively new source for high-quality aquamarines, often with intense color comparable to Pakistani stones.
Mozambique & Afghanistan: Other important producers with increasing significance in the international gemstone market.
Care & Handling
Cleaning: Lukewarm water with mild soap and a soft brush are ideal. Aquamarine also tolerates ultrasonic cleaning, as long as the stone has no visible cracks or liquid inclusions.
Storage: Aquamarine is more lightfast than many other gemstones – its color does not fade in sunlight. However, separate storage is recommended to prevent scratches from harder stones (sapphire, diamond).
Temperature: Aquamarine tolerates normal everyday temperatures without problems. Relevant issues usually only arise with strong, unusual temperature extremes.
Hardness: With a Mohs hardness of 7.5–8, aquamarine is well-suited for everyday wear and is excellent for rings and other jewelry worn daily.
Uses & Applications
Jewelry: Aquamarine is one of the most classic gemstones for upscale jewelry. Particularly popular in step-cut, oval, and pear shapes. Its clear transparency and light color make it ideal for large, striking stones in pendants and cocktail rings.
Collector's Items: Well-formed rough crystals with natural terminations are highly sought after by mineral collectors. Especially specimens with crystals on matrix (host rock) fetch top prices.
Market Price Logic: For faceted jewelry, aquamarine is predominantly traded per carat; larger rough crystals and collector's specimens, however, are valued per piece.
Engagement Rings: Aquamarine is gaining popularity as an alternative to diamonds in engagement rings – its hardness and durability make it suitable for this purpose.
History: Seafarers wore aquamarine as a protective stone on their voyages. The name "aqua marina" (seawater) reflects the ancient belief that the stone protects its wearer on the water.
Glossary
Important technical terms related to aquamarine and beryl mineralogy.
- Eye-clean (EYE-kleen)
A gemological term for gemstones that show no visible inclusions to the naked eye. Aquamarine is often eye-clean – a quality feature that increases its value.
- Beryl (BER-uhl)
A mineral group with the formula Be₃Al₂Si₆O₁₈. Pure beryl is colorless – trace elements create the different varieties: aquamarine (iron, blue), emerald (chromium, green), morganite (manganese, pink), heliodor (iron, yellow).
- Refractive Index (re-FRAK-tiv IN-deks)
Measures how much a stone bends light as it enters. Aquamarine has a refractive index of 1.577–1.583. This characteristic helps gemologists to uniquely identify the stone and distinguish it from similar stones (e.g., blue topaz).
- Mohs Hardness (MOHZ HARD-nes)
A scale from 1 (talc) to 10 (diamond) used to determine the scratch hardness of minerals. Aquamarine has a Mohs hardness of 7.5–8, making it harder than quartz and well-suited for jewelry.
- Pegmatite (PEG-ma-tight)
A coarse-grained igneous rock that forms in the final cooling phase of granitic magma. Pegmatites are the most important localities for beryl crystals, as slow crystallization allows for particularly large specimens.
- Pleochroism (plee-oh-KRO-iz-uhm)
The property of a crystal to show different colors or color intensities depending on the viewing direction. Aquamarine shows weak to distinct pleochroism from near colorless to blue – an important authenticity feature.
- Santa Maria (SAN-tah mah-REE-ah)
Designation for the finest color quality in aquamarine – an intense, rich blue without greenish tones. Named after the Santa Maria de Itabira mine in Minas Gerais, Brazil, where this quality was first found in larger quantities.
Further Reading
For those who want to delve deeper:
- . "Gemstones of the World". BLV Buchverlag (2020), pp. 94–99.
- . "Which Stone Is That?". Kosmos Verlag (2019), pp. 68–71.
- Mindat.org – Aquamarine – Hudson Institute of Mineralogy. International mineral database with localities and photos.
- GIA – Aquamarine Quality Factors – Gemological Institute of America. Quality criteria for aquamarine (color, clarity, cut).
