Gemstone Knowledge
SOOKJAI KNOWLEDGE
Gemstone Knowledge
A considered guide to gemstones — from colour and cut to origin, treatment and the stories behind each stone.
Colour · Spinel
Grey Spinel: Understanding Tone, Undertone and Character
Grey spinel is far more varied than one neutral shade. Learn how light-to-dark tone, blue or violet undertones, lighting, cut and metal context shape the character of grey spinel—and why there is no single best grey.
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Spinel · Treatment
Natural Spinel: Is Spinel Usually Treated?
Natural spinel is commonly encountered without treatment, but spinel can still be heated, fracture-filled or subjected to specialised diffusion treatments. Learn what is common, what has been documented, and why untreated status should be understood rather than assumed.
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Spinel
What Is Spinel?
Spinel was mistaken for ruby for centuries, but it is a distinct gemstone with its own mineral identity, colours and market. Learn what spinel is, why it comes in so many hues, how durable it is, why treatment is relatively uncommon, and why fine spinel now stands firmly on its own.
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Sapphire · Colour
Madagascar Sapphire: Colour, Character and Origin
Madagascar sapphire spans far more than one familiar look. Explore the blue-green character traders sometimes associate with the origin, its wide range of sapphire colours, the brighter character seen in some Madagascar rubies, and why appearance alone cannot establish where a stone came from.
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Origin · Other Gemstones
Siam Ruby: The Story Behind Thailand’s Historic Ruby Name
Siam Ruby is a historic name connected with the ruby fields of eastern Thailand. Explore its purplish-red association, the Chanthaburi-Trat deposits, the decline of large-scale mining and how local ruby helped shape Thailand into a major coloured-stone centre.
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Sapphire · Origin
Kashmir Sapphire: Why It Became So Famous
Kashmir sapphire became famous through a remarkable 19th-century discovery, a brief period of important production, celebrated velvety blue material and extremely limited later supply. Explore the history behind the reputation, how laboratories approach Kashmir origin, and why rarity does not decide personal preference.
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Sapphire · Origin
Burmese Sapphire: Understanding Its Reputation and Rarity
Burmese sapphire carries a long reputation shaped by Mogok, exceptional historic material and collector interest. Learn what Myanmar origin really tells us, why fine examples can be rare, how laboratories approach origin, and why a famous source does not determine the beauty of an individual stone.
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Sapphire · Origin
Sri Lankan Sapphire: What Makes Ceylon Sapphire Distinctive?
Ceylon Sapphire refers to sapphire from Sri Lanka, but origin does not define one shade of blue or guarantee a particular appearance. Explore Sri Lanka’s long gem history, alluvial deposits, colour diversity, geuda, treatment and how laboratories approach geographic origin.
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Sapphire · Colour
Why Sapphire Colour Changes Under Different Lighting
The same sapphire can look different in daylight, studio light and warm indoor lighting without the stone itself changing. Learn how illumination, brightness, colour zoning and camera processing affect the colour we see—and why this is not automatically the same as colour-change sapphire.
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Sapphire · Colour
Parti Sapphire: When More Than One Colour Shares a Stone
Parti sapphire makes visible colour zoning part of the stone’s character. Learn how different colours form within one sapphire, how cutting changes the pattern we see, why teal and parti can overlap, and how colour distribution can shape a jewelry design.
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Sapphire · Colour
Cornflower Blue Sapphire: What Defines the Colour?
Cornflower Blue is more than a lighter version of Royal Blue. Explore its historic association with Kashmir sapphire, vivid and often velvety character, laboratory terminology, and what the name does—and does not—tell you.
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Sapphire · Colour
Teal Sapphire: Understanding Blue-Green Sapphire
Teal sapphire sits where blue and green meet, but there is no single teal shade. Explore blue-dominant, balanced and green-dominant characters, colour zoning, parti sapphire, lighting, origin and how teal works in jewelry.
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