Name:

Category or Family:

Refractive Index:

Specific Gravity:

Chemical Formula:

(Periodic Table...)

Hardness:

(Mohs)

Colours:

Agate

Quartz

1.530 - 1.540

2.58 - 2.64

SiO2

(Silicon Dioxide)

[Silica]

7

White, Grey, Light Blue, Orange, Red, Black

Abalone

Organic

1.52 - 1.56

2.60 - 2.78

CaCO3

(Calcium Carbonate)

3 - 4

Iridescent

Alexandrite

Chrysoberyl

1.745 - 1.754

3.5 - 3.84

BeAl2O4

(Beryllium Aluminium Oxide)

8.5

Green/Red

(Colour change)

Amethyst

Quartz

1.552 - 1.554

2.65

SiO2

(Silicon Dioxide) [Silica]

7

Purple/Violet

Ametrine

Quartz

1.544 - 1.553

2.66

SiO2

(Silicon Dioxide) [Silica]

7

Purple & Yellow/Orange

(Dual Colour)

Ammolite

Ammonite Shell

1.52 - 1.67

2.8

CaCO3

(Aragonite Polymorph)

4.5 - 5.5

Red/Green (Iridescent)

Andalusite

1.634 - 1.643

3.13 - 3.21

Al2SiO5

(Aluminium Nesosilicate)

7 - 7.5

Brown, Yellow, Green (Rare: Pink, Violet & Red)

Aquamarine

Beryl

1.577 - 1.583

2.72

Be3Al2(SiO3)6

8

Blue/Turquoise

Beryl

Silicate Mineral

1.577 - 1.583

2.67 - 2.84

Be3Al2(SiO3)6

7.5-8

Green, Blue, Yellow, Clear, Pink & Others

Bloodstone

Quartz

1.53 - 1.54

2.61

SiO2

(Silicon Dioxide)

6.5 - 7

Green with Red Inclusions

Carnelian

Quartz

1.564  -1.660

2.65

SiO2

(Silicon Dioxide)

7

Reddish Brown

Chrome Diopside

1.693 - 1.728

3.25 - 3.55

MgCaSi2O6

5.5 - 6.5

Green

Chrysoberyl

Beryllium

1.746 - 1.755

3.5 - 3.84

BeAl2O4

8.5

Green, Yellow, Brown & Red

Chrysocolla

Silicate Mineral

1.460 - 1.570

1.9 - 2.4

(Cu,Al)2H2Si2O5(OH)4-nH2O

2-4

Blue/Green

Citrine

Quartz

1.544 - 1.553

2.66

SiO2

(Silicon Dioxide)

7

Yellow - Orange

Coral

Organic

1.486 - 1.658

2.65

CaCO3

(Calcium Carbonate)

3.5-4

Red, Orange, Pink, Peach, Black, Brown, Metallic Gold.

Corundum

Hematite

1.762 - 1.770

3.97 - 4.03

Al2O3

(Aluminium Oxide)

9

All Colours

Cubic Zirconia

Synthetic

2.15

5.60 - 6.00

ZrO2

(Zirconium Oxide)

8 - 8.5

All Colours

Demantoid

Garnet

1.880 - 1.889

3.84

Ca3Fe2Si3O12

6.5

Green

Diamond

Carbon

2.417

3.49 - 3.55

C

(Carbon)

10

Wide variety of colours

Emerald

Beryl

1.576 - 1.582

2.7 - 2.78

Be3Al2(SiO3)6

(Beryllium Aluminium Silicate)

7.5 - 8

Green

Feldspar

Tectosilicate

1.560 - 1.570

2.5 - 2.8

KAlSi3O8 or NaAlSi3O8 or CaAl2Si2O8

(Variety dependant)

6

Pink, White, Gray, Brown

Fire Opal

Mineralite

1.42 - 1.43

2.15

SiO2-nH2O

(Hydrated Silica)

5.5 - 6.5

Full Spectrum

(Iridescent)

Garnet

Nesosilicates

1.72  - 1.94

3.1 - 4.3

X3Y2(SiO4)3

6 - 7.5

All colours

Hematite

Oxide Mineral

Opaque

4.9 - 5.3

Fe2O3, a-Fe2O3

(Iron (III) Oxide)

5.5 - 6.5

Metallic Grey - Earthy Red

Iolite

Mineral

1.522 - 1.558

2.57 - 2.66

(Mg,Fe)2Al4Si5O18

7 - 7.5

Blue, Violet, Yellow-Brown

Jade

Silicate Mineral

1.660 - 1.680

3.34

NaAlSi2O6

6.5 - 7

Mainly Green, But All colours are available

Jasper

Quartz

1.564 - 1.660

2.65

SiO2

(Silicon Dioxide)

7.0

Red & Orange

Jet

(Lignite)

Coal

1.660

1.32

KNa2(Fe,Mn,Al)2

Li3Si12O30

2.5 - 4

Black

Kunzite

Spodumene

1.660 - 1.676

3.18

LiAl(Si2O6)

(Lithium Aluminium Silicate)

6.0 - 7.0

Pink

Lapis Lazuli

Lazurite

1.5

2.7 - 2.9

(Na,Ca)8(AlSiO4)6

(S,SO4,CL)1-2

5 - 5.5

Blue (With White speckles)

Malachite

Carbonate Mineral

1.875 - 1.909

3.6 - 4

CuCO3.Cu(OH)2

3.5 - 4

Bright Green to Blackish Green

Moonstone

Feldspar

1.52 - 1.54

2.55 - 2.58

KALSi3O8

6 - 6.5

Grey, White, Pink, Green, Brown & Blue

Morganite

Beryl

1.577 - 1.583

2.72

Be3Al2(Si6O18)

7.5 - 8

Pale Pink

Obsidian

Volcanic Glass

1.48 - 1.51

2.6

SiO2 + MgO, Fe3O4

5 - 5.5

Black, Grey, Dark Green, Red, Yellow & pink

Onyx

Quartz

1.564 - 1.660

2.65

SiO2

(Silicon Dioxide)

7.0

Black (Sometimes with bands of colour)

Opal

Mineraloid Gel

1.450

2.15

SiO2H2O

5.0 - 6.5

Full Spectrum

(Iridescent)

Pearls

Organic

1.530 - 1.685

2.7

CaCO3

(Calcium Carbonate)

2.4 - 4

Most colours, Traditionally White or Black.

(Iridescent)

Peridot

Mineral

1.654 - 1.690

3.31-3.48

(Mg,Fe)2SiO4

6.5-7

Green

Pyrite

Sulphide Mineral

Opaque

4.95 - 5.10

FeS2

(Iron Disulphide)

6 - 6.8

Pale Yellow/Gold

Ruby

Corundum

1.768 - 1.772

4.0

Al2O3:Cr

(Aluminium Oxide with Chromium)

9

Red (May be brownish, purplish or pinkish)

Sapphire

Corundum

1.768 - 1.772

3.95 - 4.03

Al2O3

(Aluminium Oxide)

9

Any Colour Except Red (Ruby)

Sodalite

Sodalite

1.48 (Isotropic)

2.27 - 2.33

(Na4Al3(SiO4)3Cl)

(Sodium Aluminium Silicate with Chlorine)

5.5 - 6

Royal Blue, Green, yellow, Violet

Spinel

Spinel

1.712 - 1.762

3.54 - 3.63

MgAl2O4

8

Red, Purple, Blue, Dark Green, Brown, Black.

Sugilite

Cyclosilicate

1.607 - 1.610

2.74 - 2.8

KNa2(Fe,Mn,Al)2

Li3Si12O30

5.5 - 6.5

Amazing Purple

Sunstone

Feldspar

1.525 - 1.58

2.64 - 2.66

(Ca,Na)((Al,Si)2Si2O8)

6 - 7.2

Clear, Yellow, Red & Green

Quartz

Quartz

1.552 - 1.554

2.65

SiO2

(Silicon Dioxide)

7

Many Colours (Most are named, e.g.. Amethyst)

Tanzanite

Zoisite

1.69 - 1.7

3.10 - 3.38

(Ca2Al3(SiO4)(Si2O7)O(OH))

6.5

Purple/Blue

Topaz

Silicate Mineral

1.616 - 1.638

3.49 - 3.57

Al2SiO4(F,OH)2

8

Clear, Blue, Brown, Orange, Gray, Yellow, Green, Pink and Reddish

Tourmaline

Silicate Mineral

1.612 - 1.650

3.0 - 3.26

(Ca,K,Na)(Al,Fe,Li,Mg,Mn)3

(Al,Cr,Fe,V)6

7 - 7.5

All Colours

Tsavorite

Garnet

1.740

3.6 - 3.68

Ca3Al2Si3O12

7 - 7.5

Green

Turquoise

Phosphate Mineral

1.610 - 1.650

2.6 - 2.9

CuAl6(PO4)4(OH)8-4H2O

5-6

Blue, Blue-Green, Green

Zircon

Nesosilicates

1.810 - 1.984

3.93 - 4.73

ZrSiO4

(Zirconium Silicate)

6 - 6.5

Brown, Red, Yellow, Green, Black & Clear

Zultanite

Diaspore

1.75

3.39

AlO(OH)

6.5 - 7

Colour Changing, dependant on light source.