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Spinel

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About Spinel - History and Introduction

Historical values 2005 - 2016

Spinel

Colour: red, orange, yellow, purple, blue, green, grey

Hardness: 8

Refractive index: 1.71 - 1.92

Density: 3.60 - 4.00

Chemical composition: MgAl2O4

Crystal structure: isometric

Origins: Brazil, USA, Madagascar, Sri Lanka, Burma, Thailand, Cambodia, Afghanistan, Russia.

Spinel probably is the most commonly seen sapphire imitation. The most expensive spinels are purple, red, orangey-red and blue.

Color

Color Description; Occurrence

1 ct.

3 ct.

5 ct.

10 ct.

30 ct.

215 - medium dark strongly purplish Red; very slightly brownish

Alternative name, occurrence category: Common

173.55

296.13

418.71

725.17

No data

222 - medium dark slightly purplish Red; strong

Alternative name, occurrence category: Common

298.19

508.80

719.42

1,245.96

No data

010 - medium dark Red; strong

Alternative name, occurrence category: Common

377.12

643.50

909.87

1,575.80

No data

016 - medium orangey Red; strong

Alternative name, occurrence category: Rare

1,388.39

2,369.04

3,349.70

5,801.34

No data

008 - medium Red; very slightly brownish

Alternative name, occurrence category: Rare

1,536.82

2,622.32

3,707.82

6,421.56

No data

220 - medium slightly purplish Red; strong

Alternative name, occurrence category: Rare

1,612.93

2,752.18

3,891.43

6,739.56

No data

218 - medium light slightly purplish Red; strong

Alternative name, occurrence category: Common

401.11

684.42

967.73

1,676.01

No data

203 - medium reddish Purple; very slightly brownish

Alternative name, occurrence category: Common

742.54

1,267.01

1,791.49

3,102.68

No data

209 - medium light strongly purplish Red; very slightly brownish

Alternative name, occurrence category: Common

430.76

735.01

1,039.26

1,799.90

No data

003 - light Red; very slightly brownish

Alternative name, occurrence category: Common

170.72

291.30

411.88

713.33

No data

189 - light Purple; very slightly greyish

Alternative name, occurrence category: Common

174.12

297.10

420.08

727.53

No data

165 - light bluish Violet; very slightly greyish

Alternative name, occurrence category: Common

187.33

319.65

451.97

782.77

No data

168 - medium light bluish Violet; slightly greyish

Alternative name, occurrence category: Common

237.00

404.40

571.80

990.30

No data

171 - medium bluish Violet; slightly greyish

Alternative name, occurrence category: Common

328.97

561.33

793.69

1,374.58

No data

150 - medium light Blue; slightly greyish

Alternative name, occurrence category: Common

270.62

461.76

652.90

1,130.76

No data

153 - medium Blue; slightly greyish

Alternative name, occurrence category: Common

336.90

574.86

812.82

1,407.72

No data

117 - medium very strongly bluish Green; slightly greyish

Alternative name, occurrence category: Common

260.98

445.32

629.66

1,090.51

No data

224 - very light Grey

Alternative name, occurrence category: Common

167.88

286.46

405.04

701.50

No data

227 - Grey

Alternative name, occurrence category: Common

208.30

355.42

502.55

870.36

No data

About Spinel - History and Introduction

Spinel is a hard vitreous magnesium aluminum oxide that has been used as a gemstone for centuries. The beauty of spinel has caused it to be mistaken for ruby and sapphire in the past. However, spinel deserves to be recognized as a gemstone that is worthy of appreciation in its own right. Spinel occurs in a range of colours, such as rose pink to rich red; lavender to deep violet; light to deep blue, orange, yellow, brown and black.


The name spinel is thought to have come from either the Latin word, "spina", meaning thorn, due to its pointed crystal form, or the Greek word for "spark", in reference to its bright color. Spinel has been mined for centuries and one of the most famous historical spinel gemstones is known as "the Black Prince's Ruby". As the name suggests, this is a red gemstone, which was thought to be a ruby. The "Black Prince's Ruby" was acquired by Edward, Prince of Wales in 1367. It is set into England's state crown and is held at the Tower of London.


Spinel is often assumed to be other gemstones, such as ruby and sapphire. However, spinel can be distinguished from other gemstones by its octahedral crystal structure and single refraction. Additionally, spinel has a lower Mohs hardness than ruby and sapphire.


Spinel; Origin and Gemstone Sources Back to Top

Spinel occurs with ruby and sapphire, and significant deposits have been found in Cambodia, Myanmar (Burma), Sri Lanka (Ceylon) and Thailand. Other locations where spinel deposits have been found are Afghanistan, Australia, Brazil, Madagascar, Nepal, Nigeria, Tadzhikistan, Tanzania and the USA.


Buying Spinel and Determining Spinel Gemstone Value

Spinel Colour


The rarest and most desirable spinel gemstones are vivid ruby-like red, followed by cobalt blue, bright pink and bright orange. Paler colours such as lavender tend to be more affordable. Other colours are black, violet-blue, greenish-blue, grayish, pale-pink, mauve, yellow and brown.


Spinel Clarity and Luster


Good quality spinel gemstones should have no visible inclusions. Inclusions typically decrease the value of spinel gemstones. However, desirable inclusions can result in asterism (the star effect). Inclusions in spinel can resemble its octahedral crystal structure or a human fingerprint. Spinel has a vitreous luster.


Spinel Cut and Shape


Spinel can be seen in faceted shapes such as octagons, trillions, squares, rounds and fancy shapes, such as ovals, pears and cushions. Vividly colored spinel gemstones are rare in sizes over 5 carats. Translucent to opaque stones are often cut en cabochon. Rare star spinel is cut en cabochon to display the asterism.


Spinel Treatment


Whilst spinel is not usually treated or enhanced, synthetic spinel is commonly produced because it can appear similar to a variety of gemstone types. Most synthetic spinel can be separated from natural spinel by the use of a magnet. Natural spinel shows a weak to moderate response to magnets due to its iron content. Some light-colored and orange spinel is coloured by chromium, which causes it to be diamagnetic (repelled by a magnet). Additionally, natural spinel exhibits an octahedral crystal structure. Natural spinel is also available and all reputable gem traders declare products as natural or synthetic.

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