| Material |
Refractive
Index |
Critical
Angle |
Birefringenge |
Dispersion |
Hardness |
Specific
Gravity |
Crystal
System |
Class |
Formula |
Cleavage |
| Apatite series |
1.64 |
37.57° |
.004 |
.013 |
5.0 |
3.05-3.20 |
hexagonal |
6/m |
Ca5(PO4,CO3)3(F,Cl,OH) |
2; {0001}indistinct; {10-10}
trace |
| Beryl |
1.57-1.60 |
38.68-39.56° |
.006-.009 |
.014 |
7.5-8.0 |
2.60-2.90 |
hexagonal |
6/m 2/m 2/m |
Be3Al2Si6O18 |
1; {0001} indistinct |
| Color varieties of beryl include aquamarine
(blue), emerald (green), goshenite (colorless), heliodor (yellow) and
morganite (pink). |
| Chrysoberyl |
1.75 |
34.85° |
.010 |
.015 |
8.5 |
3.75 |
orthorhombic |
2/m 2/m 2/m |
BeAl2O4 |
3; {110} distinct, {010} imperfect, {001}
indistinct |
| Corundum |
1.77 |
34.40° |
.008 |
.018 |
9.0 |
4.00-4.10 |
hexagonal |
B3 2/m |
Al2O3 |
2; {0001} and {10-11} parting |
| Ruby is red corundum. All other colors of
corundum are classified as sapphires. |
| Cubic Zirconia |
2.15-2.18 |
27.30-27.72° |
.000 |
.058-.060 |
8.3-8.5 |
5.6-6.0 |
(man made) |
|
ZrO2 |
|
| Danburite |
1.63 |
37.84° |
.006 |
.016 |
7.0 |
2.97-3.02 |
orthorhombic |
2/m 2/m 2/m |
CaB2(SiO4)2 |
1; {001} indistinct |
| Diamond |
2.41 |
24.52° |
.000 |
.044 |
10.0 |
3.51 |
isometric |
4/m B3 2/m |
C |
1; {111} perfect |
| Epidote |
1.75 |
34.85° |
.047 |
.030 |
6.0-7.0 |
3.35-3.50 |
monoclinic |
2m |
Ca2(Fe,Al)3(Si2O7)(SiO4)(O,OH_2 |
6; {001} and {010} perfect, {100}, {110},
{-110} and {-201} partings |
Feldspar
Group |
1.52-1.58 |
39.23-41.12° |
.007-.013 |
.012 |
|
|
|
|
|
|
| - orthoclase |
~ |
~ |
~ |
~ |
6.0-6.5 |
2.55-2.63 |
monoclinic |
2m |
KAlSi3O8 |
2; {11-20} and {10-11} indistinct |
| - labradorite |
~ |
~ |
~ |
~ |
6.0-6.5 |
2.69-2.72 |
triclinic |
B1 |
Na.5-.3Ca.5-.7Al1.5-1.7Si2.5-2.3)8 |
3; {001} perfect, {010} and {110} nearly
perfect |
| - Sunstone (oligoclase) |
~ |
~ |
~ |
~ |
6.0-6.5 |
2.63-2.67 |
triclinic |
B1 |
70-90%(Na,Ca)Al(Al,Si)Si2O810-30%CaAl2Si2O8 |
3; {001} perfect, {010} nearly perfect, {110}
imperfect |
| Fluorite |
1.43 |
44.37° |
.000 |
.007 |
4.0 |
3.218 |
isometirc |
4/m B3 2/m |
CaF2 |
1; {111} perfect |
| Garnet Group |
| - almandine |
1.78-1.81 |
33.54-34.18° |
.000 |
.024 |
7.0-7.5 |
4.10-4.30 |
isometric |
4/m B3 2/m |
Fe3Al2(SiO4)3 |
1; {110} parting sometimes
distinct |
| - andradite |
1.85-1.89 |
31.94-32.74° |
.000 |
.057 |
6.5-7.0 |
3.70-4.10 |
isometric |
4/m B3 2/m |
Ca3Fe2(SiO4)3 |
|
| - grossular |
1.73-1.74 |
35.08-35.31° |
.000 |
.027 |
6.5-6.7 |
3.40-3.60 |
isometric |
4/m B3 2/m |
Ca3Al2(SiO4)3 |
1; {110} parting |
| - pyrope |
1.73-1.76 |
34.62-35.31° |
.000 |
.022 |
7.0-7.5 |
3.50-3.80 |
isometric |
4/m B3 2/m |
Mg3Al2(SiO4)3 |
1; {110} parting sometimes
distinct |
| - spessartine |
1.79-1.81 |
33.54-33.96° |
.000 |
.027 |
7.0-7.5 |
3.80-4.25 |
isometric |
4/m B3 2/m |
Mn3Al2(SiO4)3 |
1; {110} parting sometimes
distinct |
| - uvarovite |
1.87 |
32.33° |
.000 |
|
6.5-7.0 |
3.40-3.80 |
isometric |
4/m B3 2/m |
Ca3Cr2(SiO4)3 |
|
| Glass |
1.44-1.68 |
36.53-43.98° |
|
|
4.0-7.0 |
2.2-5.0 |
(man made) |
|
higly variable |
|
| Iolite (cordierite) |
1.55 |
40.18° |
.017 |
.017 |
7.0-7.5 |
2.53-2.78 |
orthorhombic |
2/m 2/m 2/m |
Mg2Al4Si5O18 |
3; {010} distinct, {001} and {100}
indistinct |
| Opal |
1.45 |
43.60° |
.000 |
|
5.5-6.5 |
1.99-2.25 |
(amorphous) |
|
SiO2(nH20) |
|
| Peridot (forsterite) |
1.67 |
36.78° |
.038 |
.020 |
7.0 |
3.28 |
orthorhombic |
2/m 2/m 2/m |
Mg2SiO4 |
2; {010} and {100} imperfect |
| Quartz |
1.54 |
40.49° |
.009 |
.013 |
7.0 |
2.66 |
hexagonal |
32 |
SiO2 |
7;
{10-11}{01-11}{10-10}{0001}{11-20}{11-21}{51-61} indistinct |
| Scapolite series |
1.58 |
39.27° |
.022 |
|
5.5-6.0 |
2.50-2.78 |
tetragonal |
4/m |
(Na,Ca)4Al3Si9O24Cl |
2; {100} and {110} distinct |
| Sphene (titanite) |
1.99-2.03 |
29.51-30.17° |
.051 |
.051 |
5.0-5.5 |
3.45-3.55 |
monoclinc |
2/m |
CaTiSiO5 |
2; {110} distinct, {221} parting |
| Spinel |
1.72 |
35.55° |
.000 |
.020 |
7.5-8.0 |
3.58 |
orthorhombic |
4/m B3 2/m |
MgAl2O4 |
1; {111} parting indistinct |
| Tanzanite (zoisite) |
1.70 |
36.03° |
.006 |
.030 |
6.5-7.0 |
3.55 |
orthorhombic |
2/m 2/m 2/m |
Ca2Al3(SiO4)3(OH) |
2; {100} perfect, {010} imperfect |
| Topaz |
1.61 |
38.40° |
.008 |
.014 |
8.0 |
3.49-3.57 |
orthorhombic |
2/m 2/m 2/m |
Al2SiO4(F,OH)2 |
1; {001} perfect |
Tourmaline
Group |
1.62-1.65 |
37.31-38.40° |
.014-.044 |
.017 |
|
|
|
|
|
|
| - dravite |
~ |
~ |
~ |
~ |
7.0 |
3.03 |
hexagonal |
3m |
NaMg3Al6(BO3)3Si6O18(OH)4 |
2; {11-20} and {10-11} indistinct |
| - elbaite |
~ |
~ |
~ |
~ |
7.0 |
3.03-3.10 |
hexagonal |
3m |
Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 |
2; {11-20} and {10-11} indistinct |
| - liddicoatite |
~ |
~ |
~ |
~ |
7.5 |
3.02 |
hexagonal |
3m |
Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4 |
|
| - uvite |
~ |
~ |
~ |
~ |
7.5 |
3.04 |
hexagonal |
3m |
(Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 |
|
| Zircon |
1.94 |
31.03° |
.060 |
.038 |
7.5 |
4.60-4.70 |
tetragonal |
4/m 2/m 2/m |
ZrSiO4 |
2; {110} imperfect; {111}
poor |
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