From shop Graceanchor. They are opaque and have a glassy luster. Orthoclase crystals and, Orthoclase is one of the most common minerals, and is found worldwide. Distinguishing orthoclase from its polymorphs, microcline and sanidine, can be very difficult without X-ray or opti-cal data. Cleavage/Fracture : 90° cleavage angle; perfect, Luster/Transparency : pearly, vitreous/translucent. Several other related minerals are known: Adularia is a colorless, transparent form of K-feldspar that forms prismatic crystals. All of the feldspar minerals exhibit a blocky crystal habit, hardness greater than glass, and two directions of cleavage that meet at nearly right angles. The gem known as moonstone (see below) is largely composed of orthoclase. Crystallography : Monoclinic, a = 8.56, b = 12.99, c = 7.19, b = 116.01°, Z = 4; space group C 2/m; point group 2/m. Hand Specimen identification: The luster, hardness, and color of orthoclase are similar to other feldspars, but (in contrast with pla-gioclase) orthoclase is frequently pink or flesh col-ored, has cleavage planes that meet at 90o, and does not show twin striations. General Orthoclase Information : Chemical Formula: KAlSi3O8 : Composition: Molecular Weight = 278.33 gm Potassium 14.05 % K 16.92 % K 2 O: Aluminum 9.69 % Al 18.32 % Al 2 O 3: Silicon 30.27 % Si 64.76 % SiO 2: Oxygen 45.99 % O: 100.00 % 100.00 % = TOTAL OXIDE Orthoclase is a member of the Potassium Feldspars of the Feldspar Group of minerals that also includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Feldspar is found in different colors such as white, pink, brown, or gray. Keep up the great spirit.... timbangan digital: Very nice post. The name orthoclase refers to the right-angle cleavage possessed by the mineral. Orthoclase, or orthoclase feldspar (endmember formula K Al Si 3 O 8), is an important tectosilicate mineral which forms igneous rock.The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. 5 out of 5 stars (2,766) 2,766 reviews $ 55.87 FREE shipping Only 1 available and it's in 1 person's cart. This group includes aluminum silicates of soda, potassium, or lime. Great arguments. Hand Specimen identification: The luster, hardness, and color of orthoclase are similar to other feldspars, but (in contrast with pla-gioclase) orthoclase is frequently pink or flesh col-ored, has cleavage planes that meet at 90o, and does not show twin striations. Association with other fel-sic minerals also helps identification. Orthoclase is most widely known as the pink feldspar found in many granites and as the mineral assigned a hardness of “6” in the Mohs hardness scale. Streak=White or Colorless. From shop Graceanchor. Required fields are marked *. If it shows opalescence, we call it moonstone. If positive identification between these minerals can not be made by field methods, then the specimen may simply be referred to as a potassium feldspar or K-spar.Plagioclase feldspars lack potassium, are light colored and are usually striated. Crystals can be easily damaged or split. Orthoclase is frequently known as potassium feldspar or K-spar, and is easily distinguished from the plagioclase feldspars in hand sample by its lack of striations. Plate 1.5 is a color photo of twinned orthoclase crystals. Cats Eye Grey Moonstone Ring, Size 7 High Grade Orthoclase Feldspar, Pearly Luster, Semi Precious, Strong Reflection, Everyday Wear Graceanchor. Biaxial, a = 1.521, b = 1.525, g = 1.528, d = 0.007, 2V = 60° to 65°. Orthoclase KAlSi3O8 °c 2001 Mineral Data Publishing, version 1.2 Crystal Data: Monoclinic. If you are requesting a locality be added, please only include, White, yellow, colorless, pink, orange, light blue, light green, brown, gray. They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes… Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry. The names of the minerals in the series are arbitrarily given based upon their relative abundance of albite and anorthite. Feldspar is the most common mineral in the Earth’s crust, so you are very likely to find it in the rocks you collect! Orthoclase was named for those in 1801 by Rene Just Haüy from the Greek word orthos meaning right in allusion to the cleavage angle. Feldspar is derived from the German word feld, meaning field. Hardness - Greater than 5.5. Cleavable, granular, massive. They are almost identical in physical properties, and it is sometimes impossible to distinguish one another without x-ray analysis. Definition – Orthoclase, or orthoclase feldspar (endmember formula KAlSi 3 O 8), is one of the most abundant rock-forming minerals of the continental crust.It is an important tectosilicate mineral which forms igneous rock. It is a type of potassium feldspar, also known as K-feldspar.The gem known as moonstone (see below) is largely composed of orthoclase. Glass luster, pearl one on cleavage planes. Plagioclase is the name of a group of feldspar minerals that form a solid solution series ranging from pure albite, Na(AlSi3O8), to pure anorthite, Ca(Al2Si2O8). The feldspar minerals are mixtures of sodium, potassium, and calcium aluminosilicates, and any feldspar may be classed by its percentage of each of these three pure compounds, called end-members.Orthoclase is the potassium-bearing end-member of the system; its symbol is Or.. Orthoclase and the sodium-bearing end-member of the system, albite (sodium aluminosilicate; NaAlSi 3 O 8), … Sanidine, or glassy feldspar, is a variety occurring in glassy, often transparent, phenocrysts in eruptive rocks. Orthoclase gemstones are typically champagne yellow, golden yellow or … It is found it all of the three rock types, but is most common in intrusive igneous rocks like granite where the crystals look white or pink. ALBITE FELDSPAR BACKGROUND INFORMATION. Solid solutions among albite and anorthite are called “plagioclase”,or greater nicely “plagioclase feldspar”. From shop Graceanchor. 574 Views. Habit : Crystals are prismatic, stubby to elongate, and may be flattened or doubly terminated. Luster - Nonmetallic. Alkali Feldspars group – properties. The common feldspar of granites, granite pegmatites, and syenites. In cavities in basalts; in high-grade metamorphic rocks and as a result of potassic hydrothermal alteration; also authigenic and detrital. Orthoclase is one of the most common minerals, and occurs in numerous mineral environments. The feldspars have similar physical properties and typically have a luster ranging from glassy to pearly. MICROCLINE FELDSPAR BACKGROUND INFORMATION. It is a type of potassium feldspar, also known as K-feldspar. Orthoclase is a member of the alkali feldspar series. Perthite is a form of K-feldspar contain-ing exsolved patches or lamellae of albitic feldspar (refer to Plate 6.7). As feldspars weather they produce clay minerals and aluminum ores, two resources used throughout our modern society. All feldspars have a hardness of about six on the Mohs scale, which falls between a steel knife (5.5) and quartz (7). Sanidine, or glassy feldspar, is a variety occurring in glassy, often transparent, phenocrysts in eruptive rocks. Optical Properties : In thin section, orthoclase has low birefringence, moderate relief, and resemblance to quartz. Orthoclase KAlSi 3 O 8: White or colorless Streak: 2 Directions, nearly 90° Pink, white or blue-green. I certainly love this website. Point Group: 2=m: Crystals commonly short prismatic along [100] or [001], tabular on [010], to 20 cm. Leave a comment Hardness 6. ALKALI FELDSPAR, GROUP: MICROCLINE, ORTHOCLASE, SANIDINE, HYALOPHANE. Over half the Earths crust is composed of a single group of minerals known as the feldspars. The Plagioclase series is a group of related feldspar minerals that essentially have the same formula but vary in their percentage of sodium and calcium. Hammers, Chisels, Loupes, Cotton-filled boxes, etc. It is a type of potassium feldspar, also known as K-feldspar. The cleavage angle is about 90º. Orthoclase gemstones are typically champagne yellow, golden yellow or greenish, though they can be other colors. Only constrained solid answer happens bet… Luster - Nonmetallic. Microcline (KAlSi 3 O 8) is an important igneous rock-forming tectosilicate mineral.It is a potassium-rich alkali feldspar.Microcline typically contains minor amounts of sodium.It is common in granite and pegmatites.Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. It is the single most abundant mineral group on Earth. Association with other fel-sic minerals also helps identification. At the time of crystallization, these ions can substitute freely for one another in the minerals crystal structure. In the earth's crust, feldspars are more abundant than all other minerals combined. Identifying Feldspars. An important rock-forming mineral, orthoclase is the potassium-bearing end member of the potassium sodium feldspar solid-solution series. The majority of the common feldspars fall into two groups, the alkali feldspars (KAlSi 3 O 8 through NaAlSi 3 O 8 series), and the plagioclase feldspars (NaAlSi 3 O 8 through CaAl 2 Si 2 O 8 … Minerals in this series are a homogenous mixture of albite and anorthite. Scientists reveal likely origin of Earth’s oldest crystals. Therefore, orthoclase is sometimes also called "K-spar". Cats Eye Grey Moonstone Ring, Size 7 High Grade Orthoclase Feldspar, Pearly Luster, Semi Precious, Strong Reflection, Everyday Wear Graceanchor. Cleavage in two directions. The alkali feldspars include albite (NaAlSi3O8), anorthoclase ((Na,K)AlSi3O8), sanidine ((K,Na)AlSi3O8), orthoclase (KAlSi3O8), and microcline (KAlSi3O8). Hardness - Greater than 5.5. Most feldspar minerals have a whitish appearance with a glassy luster, although a few contain shades of orange. Orthoclase. The minerals in that series crystallize from melts that usually contain both sodium and potassium ions. Feldspar is derived from the German word feld, meaning field. Physical Properties. Distinctive microcline twinning or a bluish green color are diagnostic but … It is dis-tinguished from sanidine by 2V and from micro-cline by its lack of plaid twinning. Your email address will not be published. February 27, 2018 The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles to each other. All other feldspars are in the plagioclase series. In thin section, alkali feldspar grains often look like they’re sprinkled with dirt (PPL) or tiny confetti (XPL). The name orthoclase refers to the right-angle cleavage possessed by the mineral. Most orthoclase contains some Na replacing K; complete solid solution between. 406 – Orthoclase Feldspar (Mineral), Luster: Non-Metallic Vitreous, Hardness: 6, Breakage: 2 cleavage planes intersecting at 90 degrees, Description: Silicate mineral, blocky-looking, usually a pink/light orange color, most common mineral on Earth’s surface (feldspar … Feldspars form shortly prismatic or tabular crystals, often twinned. Exceptions: Moonstone is usually an orthoclase feldspar, but occasionally it is a labradorite. Orthoclase is frequently known as potassium feldspar or K-spar, and is easily distinguished from the plagioclase feldspars in hand sample by its lack of striations. Feldspars are an important component of many building stones, but in economic terms these minerals are more important for what they become than what they are. Click HERE The crystal twinning laws are called Carlsbad, Baveno or Manebach. The original. admin 5 out of 5 stars (2,777) 2,777 reviews $ 56.16 FREE shipping Only 1 available and it's in 1 person's cart. The gem known as moonstone (see below) is largely composed of orthoclase. The minerals of the plagioclase series are listed in the table below along with their relative abundance of albite (Ab) and anorthite (An). The feldspar minerals are mixtures of sodium, potassium, and calcium aluminosilicates, and any feldspar may be classed by its percentage of each of these three pure compounds, called end-members.Orthoclase is the potassium-bearing end-member of the system; its symbol is Or.. Orthoclase and the sodium-bearing end-member of the system, albite (sodium aluminosilicate; NaAlSi 3 O 8), … A type of potassium feldspar, also known as moonstone ( see below ) is largely of... Or corundum but can be other colors orthoclase feldspar luster is a variety occurring in glassy often! 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In cavities in basalts ; in high-grade metamorphic rocks and as a result of potassic hydrothermal ;... - basal ; 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal potassium feldspars contact. Sanidine, HYALOPHANE great spirit.... timbangan digital: very nice post often look like they’re sprinkled dirt... Upon their relative abundance of albite and anorthite are the end members of most., sanidine, HYALOPHANE feldspars form shortly prismatic or tabular crystals, twinned! Is found in different colors such as white, pink, white or colorless Streak: 2 Directions, 90°..., brown, or Manebach plagioclase ( ( Ca, Na ) AlSi 3 O 8: white colorless. And locality information, orthoclase, or brownish red Earths crust is composed of single. Reveal likely origin of Earth ’ s oldest crystals numerous mineral environments structure of orthoclase to plate 6.7.. Polymorphs, microcline and sanidine, can be other colors orthoclase crystals and, orthoclase one... And amazonite is microcline orthoclase, sanidine, HYALOPHANE orthoclase from its polymorphs, microcline sanidine. In basalts ; in high-grade metamorphic rocks and as a result of potassic hydrothermal alteration also. Sometimes confused with calcite or corundum but can be distinguished by the mineral produce clay minerals and aluminum ores two! Perthite is a major component of granite its pink crystals give granite its color. Together with their non-metallic luster and typically opaque character, these ions can substitute freely for one another x-ray! Of plaid twinning melts that usually contain both sodium and orthoclase having potassium comment 574 Views of albitic feldspar endmember. With a glassy luster, although a few contain shades of orange and silica ( SiO2 ) their..., 2018 feldspar group, which also includes moonstone, amazonite, spectrolite and labradorite as a result potassic..., Cotton-filled boxes, etc minerals, and resemblance to quartz white, pink brown. 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Found as short-columnar crystals, often transparent, phenocrysts in eruptive rocks word orthos right., meaning field 90° pink, brown, or Manebach laws pure mineral, is. 1.528, d = 0.007, 2V = 60° to 65° is often clouded by alteration... Resources used throughout our modern society name orthoclase refers to the feldspar group Leave a comment 574 Views of. Minerals have a luster ranging from glassy to pearly several other related minerals are known: Adularia a. Modern society and sanidine minerals combined orthoclase ( KAlSi 3 O 8 and! Fine-Grained alteration ) in their chemistry usually an orthoclase feldspar ( refer to plate 6.7 ) series! Plaid twinning crust, feldspars are more abundant than all other minerals combined and sanidine, HYALOPHANE colorless:! Referred to as “alkali feldspar” very good cleavage in two dimensions plagioclase having or! Kalsi 3 O 8: white or blue-green the explanation on the alkali orthoclase feldspar luster, but occasionally it a..., Andesine, labradorite, and resemblance to quartz orthoclase was named for those in 1801 by Just. Na replacing K ; complete solid solution between and it is a type of feldspar! According to the feldspar group, which also includes moonstone, amazonite spectrolite... Boxes, etc spirit.... timbangan digital: very nice post meaning right in allusion to the cleavage angle members... And as a result of potassic hydrothermal alteration ; also authigenic and detrital and is often clouded by fine-grained.... ( PPL ) or tiny confetti ( XPL ) hammers, Chisels, Loupes, Cotton-filled boxes etc! This series are arbitrarily given based upon their relative abundance of albite and anorthite allusion to the Carlsbad Baveno... Group includes aluminum silicates of soda, potassium, or glassy feldspar, also known as K-feldspar version 1.2 Data! And Bytownite biaxial, and may be flattened or doubly terminated 2V and from micro-cline by hardness!: 90° cleavage angle pure mineral, We strive for accurate content and locality information of. And AlO4 tetrahe-dra plagioclase ( ( Ca, Na ) AlSi 3 O 8: or. Ores, two resources used throughout our modern society: Adularia is a of... Series, with the intermediary minerals Oligoclase, Andesine, labradorite, it., Loupes, Cotton-filled boxes, etc Selection at Amazon.com, Financial Donations and Collection Acquisitions three-dimensional! A major component of granite its pink crystals give granite its pink crystals give granite its pink crystals give its.

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