Blue John

Q: What is Blue John?

O Blue John é uma variedade ornamental muito rara de fluorite, encontrada exclusivamente nas cavernas de Blue John e Treak Cliff Hill, perto de Castleton, no Derbyshire, Inglaterra. Apresenta bandas características de cor violeta-azulada alternadas com branco e amarelo, criando padrões curvos únicos

Q: What is the hardness of Blue John?

Blue John has a Mohs hardness of 4.0, making it relatively soft for use in jewelry.

Q: What color is Blue John?

Blue John is primarily Various.

Q: How much does Blue John cost?

Blue John falls into the Budget (< $50/ct) price range. Prices vary based on color, clarity, cut, and origin.

Q: What is the crystal system of Blue John?

Blue John belongs to the Isometric crystal system.

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Physical & Optical Properties

Category Semi-Precious Gems

Mohs Hardness 4,0

Specific Gravity 3,0 – 3,25

Refractive Index 1,432 – 1,436

Crystal System Isometric

Luster Vitreous

Cleavage Perfect

Color various

Mohs Hardness

Mohs hardness of Blue John shown against the ten reference minerals, from talc (1) to diamond (10).

Mohs	Reference mineral	Blue John
1	Talc
2	Gypsum
3	Calcite
4	Fluorite	●
5	Apatite
6	Orthoclase
7	Quartz
8	Topaz
9	Corundum
10	Diamond

Crystal System

Value & Market

Price Tier Budget (< $50/ct)

Where to Buy Blue John

Blue Nile Fine jewelry retailer

James Allen Gemstone jewelry

Brilliant Earth Ethically sourced gems

Amazon Wide selection

Links may earn a commission at no extra cost to you.

Treatments

4Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) 3.00 to 3.25Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) PerfectHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) 1.432 to 1.436Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) IsotropicUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Banded white/purpleGemdat.org, Management Team (2012) Transparent,TranslucentArthur Thomas, Gemstones (2009) VitreousArthur Thomas, Gemstones (2009) IsometricHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Cubic, massiveArthur Thomas, Gemstones (2009) Blue John information at mindat.org UK  [www.thamesvalleyminerals.com] Fluorite: The Collector's Choice. Extra Lapis English No. 9

About Blue John

O Blue John é uma variedade ornamental muito rara de fluorite, encontrada exclusivamente nas cavernas de Blue John e Treak Cliff Hill, perto de Castleton, no Derbyshire, Inglaterra. Apresenta bandas características de cor violeta-azulada alternadas com branco e amarelo, criando padrões curvos únicos que resultam de fracturas antigas preenchidas com fluorite de diferentes composições. Tem sido utilizado em objectos decorativos e joalharia inglesa desde o século XVIII, e é tão raro que a produção anual é limitada. É considerado um verdadeiro tesouro geológico britânico.

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