Comments. Translucent albite is sometimes found that is colored a rich green by inclusions of chrome-rich jadeite. Albite is sometimes intergrown with emerald, especially in the strange hexagonal skeletal crystals known as trapiche emeralds. Facetable albite from Madagascar has indices: a = 1.530-1.531; β= 1.532-1.533; γ= 1.539-1.540; birefringence 0.009-0.010; density 2.62.
· Feldspars vary in color from pink to gray, and are categorized by the additives they contain. Pure potassium feldspar is orthoclase (KAlSi 3 O 8), pure sodium feldspar is albite (NaAlSi 3 O 8), and pure calcium feldspar is anorthite (CaAl 2 Si 3 O 8). A feldspar may contain both sodium and calcium or sodium and potassium.
Mineral Group: Feldspar group, plagioclase series. Occurrence: A major constituent of granites and granite pegmatites, alkalic diorites, basalts, and in hydrothermal and alpine veins. A product of potassium metasomatism and in low-temperature and low-pressure metamorphic facies and in some schists. Detrital and authigenic in sedimentary rocks.
· Albite (NaAlSi 3 O 8), anorthite (CaAl 2 Si 2 O 8) and K-feldspar (microcline, sanidine, orthoclase; KAlSi 3 O 8) are the major feldspar minerals that are abundant in various geological ...
Andesine was named after its original occurrence in the Andes Mountains of South America. Andesine belongs to the Plagioclase Feldspar group, an isomorphous solid solution series. Albite is one member, containing sodium and no calcium. The other end member, Anorthite, contains calcium and no sodium.Andesine is an intermediary member of this series.
Oligoclase - A plagioclase feldspar with an Albite: Anorthite molar ratio ranging from 90:10 to 70:30. Orthoclase - A monoclinic Potassium Feldspar. Adularia - A gemmy colourless variety of Orthoclase. Moonstone - A variety of Orthoclase that exhibits a strong blue adularescence.
Albite is a common felspar and is the "pivot" mineral of two different feldspar series. It is most often associated with the plagioclase series where it is an end member of this series. The plagioclase series comprises felspars that range in chemical composition from pure NaAlSi 3 O 8 to pure CaAl 2 Si 2 O 8 .
Constructing a phase diagram for feldspar weathering Below is a list of aluminosilicate minerals formed from weathering of K-feldspar. Note that many of the minerals formed in the real-world weathering environment have complicated structures and compositions. The phases listed below are simple analogs for these minerals. Remember also that most of
Albite Moonstone: Analbite (of Winchell) Anorthoclase with less than 10% KAlSi3O8: Andesine: A plagioclase feldspar with an albite : anorthite molar ratio ranging from 50 : 50 to 70 : 30. Originally described from Marmato Mine, Marmato, Cauca, Chocó Department, Colombia. Crystals are rare, to 2 cm; commonly massive, cleavable, or granular.
Chemical Weathering of Feldspars. Albite Jadeite + Quartz dΔG = ΔVdP - ΔSdT and G, S, V values for albite, jadeite and quartz to calculate the conditions for which ΔG of the reaction: Ab = Jd + Q ΔG = 0 •from G values for each phase at 298K and 0.1 MPa calculate ΔG
Feldspar - Feldspar - Identification of specific feldspars: Alkali feldspars can often be distinguished from plagioclase feldspars because most grains of the latter exhibit albite twinning (see above Crystal structure), which is manifested by parallel lines on certain cleavage surfaces, whereas grains of alkali feldspars do not. This criterion is not, however, absolute; some plagioclase ...
The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses): Albite (0 to 10) NaAlSi3O8, Oligoclase (10 to 30) (Na,Ca)(Al,Si)AlSi2O8, Andesine (30 to 50) NaAlSi3O8—CaAl2Si2O8, Labradorite (50 to 70) (Ca,Na)Al(Al,Si)Si2O8, Bytownite (70 to 90) (NaSi,CaAl)AlSi2O8, Anorthite (90 to 100) CaAl2Si2O8.. Production and Uses of Feldspar Minerals
Feldspar minerals make up over 50% of Earth''s crust.
Moonstone. (K, Na) AlSi3O8. Moonstone is a variety of albite feldspar, which is a sodium aluminum silicate. Moonstones can occur colorless,white,blue white,and pale shades of peach and apricot. The rarest and most expensive will be colorless with a floating blue color that seems to hover above the stone. This phenomenon is termed adularescence.
K may enter plagioclase and Na the orthoclase structure. These are called ternary, (three component,) feldspars. Albite/orthoclase and albite/oligoclase mixtures are possible in the same crystal, which are called perthites. Sunstone, moonstone and peristerite are examples of albite/oligoclase feldspars.
The feldspar minerals are the most common minerals in the earth''s crust. They are aluminosilicates of potassium, calcium, and sodium. The feldspars are divided into two groups, the alkali feldspars and the plagioclase feldspars. The plagioclase series is a solid solution series. The alkali feldspars are mainly potassium feldspar and albite.
Ca-Feldspar Na-Feldspar K-Feldspar Quartz Silicate minerals formed at low temperatures Slow weathering. What affects chemical weathering? • Temperature • Precipitation w e a t h e r i n g r a t e t e m p e ra t u re p r e c i p i t a t i o n. What affects chemical weathering? • Acids Weathering of Na-feldspar (albite) to kaolinite: albite ...
Plagioclase feldspars are the most common rock forming mineral on earth and form the ground-mass of many mafic, felsic, and intermediate rock. Sodium rich plagioclase or albite is present in more felsic rocks and is associated with alkali feldspar, mica, quartz, and many other minerals.
Fig. 2: Phase diagram for Or-free plagioclase feldspars at atmospheric pressure. Modified from Deer, W. A. (2001). In thin section, plagioclase commonly shows the characteristic albite polysynthetic twinning. This twinning is the most characteristic identifying feature of plagioclase, and makes its identification easy when present.
Feldspar group minerals form the continuous series of crystallization in owen''s Reaction Series. The series begins with high-temperature, calcium-rich feldspars, anorthite in its purest form. At lower temperatures, the composition evolves to intermediate sodium-rich feldspars (albite) to potassium-rich, felsic, feldspars (orthoclase).
Prewitt C T, Sueno S, Papike J J, American Mineralogist, 61 (1976) p.1213-1225, The crystal structures of high albite and monalbite at high temperatures, T = 24 deg C, feldspar View Additional jPOWD Structure files for Albite
Feldspar Group Feldspars are the most abundant minerals in the crust. The compositions of most feldspars can be represented by the ternary system anorthite (CaAl2Si2O8)—albite (NaAlSi3O8)—orthoclase (KAlSi3O8). Certain compositions within this system can only be attained at elevated temperatures, and consequently
Blum A E (1994) Feldspars in weathering, in I. Parson (ed.), Feldspars and their reactions Kluwer Academic Dordrecht, the Netherlands 595-630 Downs R T, Hazen R M, Finger L W (1994) The high-pressure crystal chemistry of low albite and the origin of the pressure dependency of Al/Si order-disorder, American Mineralogist, 79, 1042-1052 [view file]
· The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses): Albite (0 to 10) NaAlSi3O8, Oligoclase (10 to 30) (Na,Ca)(Al,Si)AlSi2O8, Andesine (30 to 50) NaAlSi3O8—CaAl2Si2O8, Labradorite (50 to 70) (Ca,Na)Al(Al,Si)Si2O8, Bytownite (70 to 90) (NaSi,CaAl)AlSi2O8, Anorthite (90 to 100) CaAl2Si2O8.. Production and Uses of Feldspar …
The alkali feldspars have chemical compositions that vary from potassium (K)-rich to sodium (Na)-rich and include some not so common compositions that are barium (Ba)-rich feldspars known as celsian and hyalophane. The pure end members of the alkali feldspars include orthoclase, microcline and albite.
In Developments in Geochemistry, 2007. 18.104.22.168 pH dependence of the dissolution kinetics of feldspars. Albite. Figure 6.29 shows that the dissolution rate of albite is strongly dependent upon pH and temperature. At all temperatures, from 5 to 300°C, the dissolution rate is at a minimum in the neutral range and increases in both the acidic- and basic-pH intervals.
A series between Albite and Anorthite Feldspar Group. Alternate name for the plagioclase series of feldspars. In petrology, the plagioclase series are defined based on their percentage of albite (Ab) to anorthite (An). Compositions of individual samples are usually written as An 24 Ab 76 meaning in this case that it is 24% anorthite and 76% albite.
Albite (NaAlSi3O8—usually designated Ab) and anorthite (CaAl2Si2O8—An) are end-members of the plagioclase series. Sanidine, anorthoclase, and the perthites are alkali feldspars whose chemical compositions lie between Or and Ab. As is apparent from the preceding statements, solid solution plays an important role in the rock-making feldspars.
Albite belongs to the Plagioclase Feldspar group, an isomorphous solid solution series.Albite is one end member, containing sodium and no calcium. The other end member, Anorthite, contains calcium and no sodium.The intermediary members are Oligoclase, Andesine, Labradorite, and Bytownite.Oligoclase and Andesine are considered by some to be a variety of Albite rather then a separate mineral.
โพแทสเซียมเฟลด์สปาร์ KAl Si3O8 (Potash Feldspar-Orthoclase-Microline) โซเดียมเฟลด์สปาร์ Na AlSi3O8 (Sodium Feldspar - Albite) แคลเซียมเฟลด์สปาร์ Ca Al2 Si2O8 (Calcium Feldspar - Anorthite)
What is Plagioclase? "Plagioclase" is the name of a group of feldspar minerals that form a solid solution series ranging from pure albite, Na(AlSi 3 O 8), to pure anorthite, Ca(Al 2 Si 2 O 8).Minerals in this series are a homogenous mixture of albite and anorthite. The names of the minerals in the series are arbitrarily given based upon their relative abundance of albite and anorthite.
ITA-D62 ELBAITE, K-FELDSPAR & ALBITE. SAN PIERO, ISOLA ELBA, ITALY - Close to several light pink k-feldspar crystals there is a well termianted bicolor elbaite. The elbaite is 0.8 cm. There are also several other elbaite of 2 and 5 mm spead around the specimens, partly hidden by nice white albite crystals. The feldspars are up to 1-1.5 cm across.
feldspar-rich pegmatites (type I), beryl–columbite-subtype pegmatites (type II), beryl–columbite–phosphate-subtype pegmatites (type III) and albite-type pegmatites (type IV). There is an increase in the albite content, relative to K-feldspar, with increasing pegmatite evolution.
Plagioclase feldspars are albite, oligoclase, andesine, labradorite, bytownite, and anorthite. This rock sample (alkali feldspar syenite) does not contain much more than red-colored alkali feldspar. The width of the sample from Estonia is 8 cm. Feldspars occur in many rock types, but one rock type is composed of nearly pure feldspar ...
Albite is a common felspar and is the "pivot" mineral of two different feldspar series. It is most often associated with the plagioclase series where it is an end member of this series. The plagioclase series comprises felspars that range in chemical composition …
Albite is a variety of feldspar with the chemical formula NaAlSi 3 O 8. As a feldspar, it makes up the group of the most common minerals on earth. It is also a tectosilicate, meaning it it made up of silicates. It is a clear gem that tends to have inclusions. Albite can be found in numerous countries, with the United States of America being the ...