Sky Blue Topaz vs. Aquamarine: A Gemstone Comparison

Sky Blue Topaz and Aquamarine, with their pale blue hues, are often mistaken for each other. It’s an easy mix-up to make, both gems share a cool, calming blue that evokes clear skies and tranquil waters. At first glance, they can look nearly identical, especially when set in jewellery. But while they may appear similar, they're actually quite different in terms of composition, rarity, and value.

Part of the confusion comes from how these stones are sold, especially when sellers use misleading trade names such as calling Sky Blue Topaz "Brazilian Aquamarine"! Without proper identification, it’s easy for buyers, and even jewellers, to confuse the two, particularly in lower-quality pieces or online listings where lighting and photography can play tricks on the eye.

Topaz is a more abundant gemstone than Aquamarine, and since most Sky Blue Topaz on the market is treated to achieve its vibrant colour, it has become a popular and affordable alternative. While this makes it a great option for those seeking a striking blue gemstone at a lower price, it also contributes to the frequent mix-ups between the two.

So, how can you tell them apart? Whether you're shopping for a jewellery creation or adding to your gemstone collection, knowing the key differences is essential. From colour variations to durability, this guide will break down everything you need to make an informed purchase so you can confidently choose the gemstone that’s right for you.

How to Tell the Difference: Visual & Gemmological Tests

Visual Clues

• Sky Blue Topaz: Bright, uniform blue with no green undertones, usually free of inclusions.
• Aquamarine: Softer, more natural blue, often with a greenish tint. Usually inclusion-free but more prone to inclusions than topaz, especially in larger cut gems.

Gemmological Tests

Test	Sky Blue Topaz	Aquamarine
Refractive Index (RI)	1.609–1.643	1.577–1.583
Birefringence	0.008–0.016	0.005–0.009
Pleochroism	Three colours (blue, pale blue, colourless)	Two colours (blue, greenish blue)
UV Fluorescence	Sometimes weakly responsive	Always inert
Optical Character	Doubly refractive, biaxial positive	Doubly refractive, uniaxial negative

Colour

• Sky Blue Topaz: Bright, uniform, medium-light blue with no green or grey undertones.
  
• Aquamarine: Ranges from pale blue to deep sea-blue, sometimes with a slight greenish tint. Deeper blues are rarer and more valuable.

Clarity & Inclusions

• Sky Blue Topaz: Typically eye-clean, with very few inclusions due to its formation and treatment. It lacks hollow growth tubes.
  
  
• Aquamarine: Generally eye-clean but may contain long, hollow tubes or liquid inclusions. Higher-quality stones have fewer inclusions.

Gemstone Formation

• Sky Blue Topaz: A silicate mineral that forms in igneous rocks. It grows in pegmatites (coarse-grained igneous rocks with large crystals) and cavities of rhyolite flows (silica-rich lava).
  
  
• Aquamarine: A blue variety of beryl that forms in granitic pegmatites. Its colour comes from trace amounts of iron.

Durability & Wearability

Scratch Resistance (Mohs Hardness Scale):

(Above 7 is suitable for everyday jewellery, while lower hardness requires more care.)

• Sky Blue Topaz: 8
• Aquamarine: 7.5–8

Cleavage & Toughness:

• Sky Blue Topaz: Perfect cleavage, meaning it can break if struck.
• Aquamarine: Imperfect cleavage, making it more durable but still requiring care.

Best Use:

Both stones work well in jewellery but should be set protectively, especially in rings.

Enhancements & Treatments

• Sky Blue Topaz: Naturally occurring Sky Blue Topaz is extremely rare. The gemstones sold commercially are almost always irradiated and heat-treated to achieve their colour.
  
  
• Aquamarine: Often heat-treated to remove greenish tones and achieve a purer blue.

Price Comparison

• Sky Blue Topaz: Affordable due to its abundance and treatment.
  • Retail prices range from £4–£16 per carat.
    
    
• Aquamarine: More expensive, particularly in deeper blues.
  • Retail prices range from £40–£400 per carat.

Size Availability

• Sky Blue Topaz: Large sizes (10+ carats) are common, with minimal price impact per carat.
  
  
• Aquamarine: Large stones exist, but high-quality material over 2 carats is rarer and significantly more expensive.

Rarity & Sourcing

• Sky Blue Topaz: Abundant due to global deposits and mass treatment. Key sources: Brazil, Russia, Pakistan, Nigeria, and the U.S.
  
  
• Aquamarine: Less common, found in smaller deposits worldwide. Key sources: Brazil, Madagascar, and Pakistan.

Cut & Shape Preferences

• Sky Blue Topaz: Often cut into standard calibrated shapes, including rounds, ovals, and emerald cuts.
  
  
• Aquamarine: Typically cut into emerald cuts and fancy shapes to enhance its clarity and colour.

Symbolic & Spiritual Associations

• Sky Blue Topaz: Associated with communication, wisdom, and mental clarity.
  
  
• Aquamarine: Linked to calming energies, courage, and protection for travellers.

Comparison Summary

Feature	Sky Blue Topaz	Aquamarine
Hardness	8	7.5–8
Cleavage	Perfect	Imperfect
Colour	Bright sky blue	Pale to deep blue, sometimes greenish
Commonly Included?	Eye-clean	Hollow tubes, liquid inclusions
Common Treatments	Irradiated + Heat	Heat
Price per Carat	£4–£16	£40–£400
Rarity	Very common	Less common
Large Sizes?	Easily available (10+ ct)	Available but expensive
Associated With	Communication, wisdom	Calming, courage

 

Sky Blue Topaz and Aquamarine are both stunning blue gemstones in their own rights that may look similar at first glance, but they differ significantly in price, rarity, and durability. Depending on your budget and preferences, both gemstones make excellent additions to a gemstone or jewellery collection!