No pleochroism. The two specimens studied come from a section along the Haast River, South Westland, where a sequence from chlorite to oligoclase-zone schist is exposed. In the thin sections examined by him,representing several of these veins from the western part of Tud-hope and the central part of James township, by far the largestproportion at least was plagioclase varying in composition fromalbite through oligoclase to andesine. Oligoclase Andesine Labradorite Bytownite Anorthite (Ca-rich end member) Plagioclase feldspars are easy to identify in thin section: they display first order grays and stripey twins. Albite twinning is fairly conspicuous and occasionally both albite and Carlsbad twinning Thin section slides are precisely ground to a thickness of 0.03 mm across the entire specimen area. Color/Pleochroism: Colorless in thin section. All thin section slides are labeled for reference. Has perfect cleavage on {001} and good cleavage on {010}. In thin section the rock consists of angular fragments and crystals of quartz, orthoclase and oligoclase-andesine and greenish yellow patches of opaline material in a very fine­ grained groundmass. Look inside the crystal to find the cleavage. In thin section, preserved ophitic and subophitic textures are observed, indicating a probable igneous origin. Mineralien-Magazin, 9/1983, 419-423.; Praetzel, I. Originally, “plane polarized” scanning in separate E-W & N-S orientations was attempted to highlight pleochroic variation, but this ultimately had to be abandoned due to significant (and very unsightly!) Before SEM analyses the thin sections were coated with a carbon layer of 15–20 nm thickness and then examined with a SEM JEOL 840 and a field emission (FE) SEM JEOL JSM 6300F, both equipped with a BSE detector and EDX spectrometer (OX2000 from Oxford Instruments, INCA system). The rhombic section, CP of the pericline twinning law, coincides with (001), CP of acline twinning law, in oligoclase to andesine. Hiraiwa and S. Yogo who helped to prepare some thin sections. Lunar Basalt. Use the Michel-Levy method to determine the composition of the plagioclase in this rock Position of Stage (degrees) Stage Rotation Stage Position when Twins Are N-S Calcite is sparingly present, associated with patches of sericite. Oligoclase has a constant com- The width of 300–500 lamellae in thin sections of an albite-twinned oligoclase (An 12) were measured at 1000 X magnification.The width distribution of the ‘white’ lamellae was always found to be different from that in the ‘black’ lamellae. Describe it. Image Courtesy of the British Geological Survey. The Plagioclase Feldspars form a series between Albite and Anorthite. Cleavages intersect at 90°. thin (fig. Difficult to see in thin section due to very low relief. What about the stuff that surrounds the plagioclase? Compare the plagioclase in this section to the plagioclase found in section … The most common accessories are apatite, magnetite, epidote, titanite, and rare zircon. Oligoclase was named in 1826 by August Breithaupt from the Greek words όλίγος and κλάσις meaning little and to break because the mineral was thought to have a less perfect cleavage than Albite.. Contrib. Shipping and handling. Wickman & Lundstr6m (1969) have madea statistical survey of lameHae widths in a cleavage piece of a pegmatite oligoclase. Smith (1974) and Tobi (1987) inferred that most (or all) of the albite-Ala B twinning law described in previous reports should be the albite law. Oligoclase is a somewhat rare variety of Albite and a member of the Plagioclase Feldspars of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone,Oligoclase, Orthoclase, Sanidine and Sunstone. Thin-section mount of oligoclase (triclinie) from Arendal, Norway, petrographic microscope slide. It can be difficult to see cleavage in thin section due to orthoclase’s low relief. Some specimens of labradorite exhibit a schiller effect, which is a strong play of iridescent blue, green, red, orange, and yellow colors when moved under a source of incident light. Thin sections (30 μm in thickness) were made for polarized transmitted light microscopy. Silver of James Township 265 feldspathic material. Find some plagioclase and describe the zoning. The sample was then coated with a 5–7 nm conductive layer of carbon. (a) full thin section, (b) mineral assemblages and (c) percentages of plagioclase. That the thick lamellae are albite and the thin oligoclase is indicated by the relative intensities of the albite-oligoclase spot pairs in both electron and X-ray diffraction patterns. a) Sample WMM‐102A‐64C1 from the Manicouagan impact structure, thin section cut normal to the striated surface and normal to shatter cone striations. Oligoclase grains contain abundant small ellipsoidal inclusions of sulfide minerals, commonly marking planes or curving surfaces in the section. The metamorphism is of upper-Jurassic, Creta-ceous age. ... 11 - Minerals in Thin Section-University of North Carolina 12 - Minerals in Thin Sections-Humboldt State 13 - Online Mineral Museum 14 - QUT Mineral Atlas 15 - Ruff.Info stray polarization effects. Right angle cleavage is characteristic. Examine the plagioclase in thin-section PLAG 1. Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Examine thin-section ANORTHITE. oligoclase-rich areas contain masses (to 500 m) of mafic minerals, sulfides and oxides, similar to the ma-fic clots that bound the oligoclase areas. Actinolite is common in greenschist-facies metabasites, and along with two other green minerals (epidote and chlorite). oligoclase zones have been established (e.g., Reed 1958; Mason 1962). 5), although there is considerable variation in the thickness of both types. Epidote, oligoclase, and A more detailed mode of the rock is unjustified, owing to the marked variation in difierent samples. This item will ship to United States, but … Thin-section studies show that the rock is composed of pale-green epidote (60-80Td, oligoclasef allophanef sericite (20-40/6) and light brown sphene (1-57d. Selection of thin sections investigated in this study. It may also be distinguished from hornblende by a lower extinction angle (typically around 15°). A little biotite is present in irregular books Make a sketch showing the zoning. Figure 8: In lava flow of yellowish brown. The weak foliation is marked with a red dashed line. Some quartz crystals show embayment and corrosion, and the fragments of quartz, which are much the commoner. Determine the optical properties of this plagioclase mineral, and complete a sample description form. In thin section, large perthitic K-feldspar megacrysts are in a hypidiomorphic granular matrix of normal to oscillatory zoned oligoclase, perthitic orthoclase-microcline, quartz, dark brown to orange-brown biotite, pinitized cordierite, and minor muscovite. Plagioclase - NaAlSi 3 O 8--CaAl 2 Si 2 O 8 Plagioclase feldspars are the most common feldspar minerals because calcium is somewhat more common in the crust than potassium (3.6 and 2.8 percent of the crust, respectively). identifiable in thin section, but clay minerals are so small (< 2 m in spherical diameter) that they can only be recognized on the basis of their crystalline structures. Abbreviations for minerals are defined in Table I of the text and Appendix Oligoclase-biotite zone, Sanbagawa terrain ltaya for his kind advice on the o r e microscopy. Moonstone is a name given to a gem material that consists of very thin, alternating layers of orthoclase (an alkali feldspar) and albite (a plagioclase feldspar). 00023. 3.2 The petrography of pyroclastic rock The petrography of pyroclastic rock displays in the Figure 9 to Figure 12, which present the petrography of full thin section, mineral assemblages and percentages of plagioclase. Thanks are also d u e t o Messrs 1. Dacite consists mostly of plagioclase feldspar and quartz with biotite, hornblende, and pyroxene (augite or enstatite).The quartz appears as rounded, corroded phenocrysts, or as an element of the ground-mass.The plagioclase in dacite ranges from oligoclase to andesine and labradorite. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series. Photographed by Michael P. Klimetz ⓘ Gossen section; H. Meixner: Der Karinthin 9:184-189 (1950) Knappenberg; Rudolfshöhe ⓘ Andreaskreuz District ⓘ Railway station dump; Groß, W. (1983) Mineralien suchen - Mineralien finden: "Wer immer grabend sich bemüht" - Mineralien von Hüttenberg / Kärnten. This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796–1872) in 1826. In the more Ca-rich The feld-spar is oligoclase and much is slightly sericitized. For viewing under polarized or transmitted light. b) Sample CHA09‐12‐01 from the … sometimes have concave edges. Mineral and rock thin sections are mounted on 27 x 46 mm microscope slides, and protected by a glass coverslip. thin-section the green color is much paler than that of hornblende. This thin section reveals that the many phenocrysts are mostly strongly zoned plagioclase. Comments: Rectangular cleavage fragment of salmon-orange oligoclase (sunstone) feldspar. Transactions . identical in oligoclase and andesine compositions (Suwa et al., 1974). Each thin section was first scanned in unpolarized light and then again between two sheets of crossed polaroid film aligned parallel to the thin section edges. In thin section some of the more granular aggregates of feld-spar show a medium- to coarse-grained, granablastic texture. Four groups of clay minerals are distinguished according to their three-dimensional arrangements of atoms: (1) the Labradorite Na0:5¡0:3Ca0:5¡0:7Al1:5¡1:7Si2:5¡2:3O8 °c 2001 Mineral Data Publishing, version 1.2 Crystal Data: Triclinic. Can be cloudy or pale brown due to inclusions. Chloritic and/or micaceous quartzofeldspathic schist predominates. Alex Strekeisen - I vetrini della mia fantasia. Seller assumes all responsibility for this listing. Plagioclase Oligoclase. In thin section it shows typical hypidiomorphic texture with euhedral oligoclase in crystals averaging .3 mm and showing fine lameHar twinning, sub-hedral orthoclase cloudy with alteration and clear anhedral quartz. Discovered in 1826; IMA status: Not Valid (variety name) They are composed of pyroxenes (diopside or augite), amphiboles (actinolite and hornblende), and plagioclases (andesine/oligoclase). of the high-pressure schist belts of New Caledonia and Sanbagawa, Japan. The thin section was later prepared for EBSD by mechanical polishing using 1 and 0.3 µm alumina suspended in distilled water for 10 min each, followed by up to 4 h on colloidal silica in an NaOH suspension.