Gemstone Knowledge
SOOKJAI KNOWLEDGE
Gemstone Knowledge
A considered guide to gemstones — from colour and cut to origin, treatment and the stories behind each stone.
Emerald
What Makes an Emerald Beautiful?
Emerald beauty is not simply the absence of inclusions. Learn how colour, transparency, jardin, cut and viewing distance work together—and why a visibly included emerald can still have remarkable presence.
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Emerald
What Is Emerald?
Emerald is the green to bluish-green variety of beryl, known for expressive colour and an internal character unlike many other gemstones. Learn what gives emerald its colour, why inclusions are common, what jardin means, and how to understand the stone on its own terms.
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Origin · Spinel
Vietnamese Spinel: Colour, Character and Origin
Vietnamese spinel is famous for the vivid cobalt-bearing blues of Luc Yen, but the origin also produces pink, red, purple and many different expressions of blue. Explore the landscape, colour range and character behind one of spinel’s most distinctive modern sources.
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Origin · Spinel
Burmese Spinel: Colour, History and Origin
Burmese spinel is known for vivid red and hot pink, but Myanmar’s spinel story is far broader than one colour or the modern Jedi name. Explore Mogok, Namya, the history behind red spinel, and why origin should not be confused with a colour grade.
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Origin · Spinel
Mahenge Spinel: Colour, Character and Origin
Mahenge is famous for vivid pink-to-red spinel with an electric, lively character, but the Tanzanian origin produces more than one colour. Explore the discovery that built its reputation, the market meaning of “Mahenge colour,” and why origin should not be confused with a quality grade.
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Colour · Spinel
Jedi Spinel: What Does the Trade Name Really Mean?
Jedi spinel is associated with some of the most vivid red-to-pink spinel in the market: saturated, bright, lively and without a heavy dark face-up appearance. Learn where the name came from, how the trade uses it, and how the more defined AIGS Type Jedi framework differs.
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Colour · Spinel
Cobalt Spinel: What Does “Cobalt” Actually Mean?
Cobalt spinel is more specific than a blue spinel that simply contains cobalt. Learn how cobalt creates blue in spinel, how iron modifies that colour, why Vietnam became important, and why laboratories consider colour, chemistry and spectroscopy together.
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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 · Sapphire
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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