Feldspar
| Feldspar | |
 feldspar crystal, discovery site: Northeast Bavaria | |
| Chemismus | (well, K, approx., Ba) (aluminium, SI) 3 O 8 |
| crystal system | triclinically or monoclinically |
| Kristallklasse | ___ |
| color | , colorless, variable white, pink, green, blue, brown |
| line color | knows |
| hardness | 6 to 6.5 |
| density | 2.5 to 2.8 |
| gloss | ___ |
| opacity | ___ |
| break | ___ |
| Fissileness | ___ |
| Habitus | ___ |
| frequent crystal faces | ___ |
| twin accomodation | ___ |
| crystal optics | |
| refraction indices | ___ |
| birefringence | ___ |
| Pleochroismus | ___ |
| optical orientation | ___ |
| angles/dispersion of the Zes-axis | 2v z ~ ___ |
| further characteristics | |
| chemical behavior | ___ |
| similar minerals | ___ |
| radioactivity | not radioactively |
| magnetism | not magnetically |
| special characteristics | ___ |
feldspar is a group very more frequently, quasi „on the field “occurring silicate - minerals of the chemical composition (well, K, approx., Ba) (aluminium, SI) 4 O 8. The elements indicated in parentheses can represent themselves mutually in each case, stand howeveralways in the same quantitative proportion to the other components of the mineral. Feldspar crystallized either in the monoclinic or in the triclinic crystal system, has a middle hardness from 6 to 6.5 and a very variable color, which know from colorless over, pink, green,blue to brown is enough.Line color is white.
Feldspar ranks among the most important rock-forming minerals.
Table of contents |
classification
feldspars leave themselves in three different groupsdivide:
- The alkali-field-late starting from-Or mixing row with the stops Albit (NaAlSi 3 O 8) and Kalifeldspat (KAlSi 3 O 8) and/or. Orthoklas/Mikroklin and the mixed crystals Anorthoklas, well-Sanidin and Sanidin have a high portion of potassium and sodium. Itare stably mixable however only at high temperatures. During the cooling it comes itself to separations, into sodium-rich lamellas into Kalifeldspat („Perthit “), and/or. in potassium-rich lamellas in Albit („Antiperthit “) express. One calls the procedure “perthitische separation”.
- Plagioklase(also lime-soda-field-late) draw for the off mixing row with the stops Albit (NaAlSi 3 O 8) and anorthite (CaAl 2 SI 2 O 8) and the mixed crystals Oligoklas, andesine, Labradorit and Bytownit against it by a large content of calcium and Sodium out.
- Ternary feldspars inside the triangle from Kalifeldspat Albit anorthite with one however at sinking temperatures increasingly large mixture gap.
The designation of a single mineral can take place also by means of percentage figures: For example one places an on merging crystal from 60 per cent of Albit and40 per cent anorthite also starting from 60 at 40 or also only briefly starting from 60 and/or. At 40 and calls it due to this composition andesine.
single minerals and Varietäten
- Albit (NaAlSi 3 O 8); triclinically
- Periklin, Cleavelandit
- andesine ((well, approx.) aluminium (SI, aluminium) 3 O 8); triclinically
- anorthite (CaAl 2 SI 2 O 8); triclinically
- Bytownit (approx., well) (SI, aluminium) 4 O 8 ; triclinically
- Maskelynit
- Labradorit (approx., well) aluminium (SI, aluminium) 3 O 8); triclinically
- Mikroklin (KAlSi 3 O8); triclinically
- Oligoklas ((well, approx.) aluminium (SI, aluminium) 3 O 8); triclinically
- Peristerit, sun stone
- Hyalophan ((K, Ba) aluminium (SI, aluminium) 3 O 8); monoclinically
- Sanidin (KAlSi 3 O 8); monoclinically
- Orthoklas (KAlSi 3 O 8); monoclinically
- To adularia, moon stone
occurrence
of feldspars arise usually in form more tafeliger or more säuliger, often verzwillingter crystals and are both in magma tables and in metamorphic and sedimentary rocks.
Which type of feldspar is in to given magma tables a rock,depends on the chemical composition and the temperature of the original melt: Potash feldspars form at comparatively low temperatures in silicon dioxide-rich magmas, which form the rocks granite and Rhyolith with the cooling. The melt is rather poor against it at silicon dioxideand crystallizes at comparatively high temperature, then develop lime soda feldspars, which are then in rocks such as Gabbro or basalt.
use as raw material
some Varietäten feldspar such as Labradorit or Orthoklas finds with suitable quality as gem stone use.
Feldspar is beside kaolin and quartz an important component during the porcelain production.
See also: List of minerals
