| MINERAL IDENTIFICATION STUDY GUIDE: Silicates (Diagnostic physical properties indicated in italics) | ||||||||||
# |
Mineral Name |
Chemical Group |
Chemical Formula |
Mohs H |
Color |
Streak |
Type Cleavage | Luster |
Acid Rx |
Other Properties |
| 19 | quartz, milky | silicates
(silica) |
SiO2 | 7 | white | none | none | vitreous | none | most common variety; usually not well crystallized |
| 28 | quartz, rock crystal | silicates
(silica) |
SiO2 | 7 | colorless | none | none | vitreous | none | 6-sided crystals; often shows conchoidal fracture |
| 1 | quartz, rose | silicates
(silica) |
SiO2 | 7 | pink | none | none | vitreous | none | usually not well crystallized |
| 14 | quartz, smokey | silicates
(silica) |
SiO2 | 7 | grey, brown | none | none | vitreous | none | amethyst variety is purple in color |
| 13
37 |
orthoclase
(K-feldspar) |
silicates
(K-feldspars) |
KAlSi3O8 | 6 | pink, red, orange, white | none | 2, at 90o | vitreous | none | large crystals are found in pegmatites |
| 33 | flint | silicates (silica) | SiO2 |
|
black, opaque | none | none | vitreous to pearly | none | often shows conchoidal fracture with sharp curved edges |
| 18 | albite,
(Na- plagioclase) |
silicates
(Ca-Na feldspars) |
NaAlSi3O8 | 6 | white or light gray | none | 2, at 90o | vitreous | none | cleavage may not be as obvious as for other feldspars |
| 10 | labradorite
(Ca- plagioclase) |
silicates
(Ca-Na feldspars) |
CaAlSi3O8 | 6 | medium to dark gray | none | 2, at 90o | vitreous | none | this variety shows blue iridescence |
| 11 | kaolinite | silicates (clays) | KAl3Si3O10(OH)2 | 1 | white | white | none | dull, earthy | none | very soft, powdery masses |
| 12 | talc | layer silicates | hydrated aluminosilicate | 1 | white | white | 1 (basal) | waxy to vitreous | none | very soft, powdery masses |
| 2 | chlorite (as chlorite schist) | silicates (clays) | Mg3Si4O10(OH)2 | 2 - 2.5 | green | white | 1 (basal) | dull to vitreous | none | found layered in metamorphic rocks |
| 6 | biotite mica | layer silicates | K(X)3Si3O10(OH)2 | 2.5 | black/brown | brown | 1 (basal) | vitreous | none | dark color even in thin sheets |
| 5 | muscovite mica | layer silicates | KAl3Si3O10(OH)2 | 2.5 | clear | white | 1 (basal) | vitreous | none | colorless in thin sheets |
| 7 | olivine
(as dunite) |
silicates
(olivines) |
(Mg,Fe)2SiO4 | 6 | green | none | none | vitreous | none | small crystals; dunite=ultramafic igneous rock |
| 26 | augite | silicates
(pyroxenes) |
complex single-chain silicate | 5 - 6 | black or dark green | none | 2, at 87o | vitreous | none | stubby crystals |
| 15 | hornblende | silicates
(amphiboles) |
complex double-chain silicate | 5 - 6 | black | none | 2, at 122o | vitreous | none | elongated crystals |
| 17 | almandine garnet | silicates (garnet) | complex silicate | 8 | dark red | none | none | vitreous | none | very hard, often found as mass of crystals |