Rocks And Minerals (F-N)

Rocks And Minerals (F-N)


Feldspar refers to a group of minerals containing aluminum and silica. They all show good cleavage in two directions at about 90 degrees. The hardness is about 6 and the specific gravity between 2.5 - 2.8.

Ferberite

Ferberite has the formulae FeWO4 - MnWO4. It has a relative hardness of 6. It is the chief ore of tungsten. A rare mineral found usually in pegmatite dikes and high-temperature quartz veins associated with granites.

Ferruginous

Ferruginous refers to containing iron.

Fire-Garnet

see "Pyrope"

Flint

Flint is a compact mineral of fine grained silica. It is a variety of quartz.

Flow banding

Flow banding refers to a structure sometimes found in volcanic rocks where alternating layers of rock have different mineral compositions.

Fluorine

Fluorine is a non-metallic element occurring naturally.

Fluorite

Fluorite has the formulae CaF2. It has a relative hardness of 4. It is found in veins where it's the main mineral or with metallic ores, especially lead and silver. Common in dolomites and limestone. Associated with many different minerals. Used chiefly as a flux in the making of steel, also for enameling, and it's used in the preparation of hydroflouric acid.

Fluorspar

Fluorspar is a natural mineral containing flourine.

Foliation

Foliation refers to a layered structure present in some metamorphic rocks which results from the segregation of different minerals into roughly parallel layers.

Franklinite

Franklinite has the formulae (Zn,Mn,Fe)(Fe,Mn)2O4 It has a relative hardness of 7. It is used as an ore of zinc and manganese. With minor exceptions, the mineral is confined to Franklin, New Jersey.

Freibergite

Freibergite is a variety of tetrahedrite containing between 28 and 36 percent silver.

Friable

Friable refers to crumbles or is pulverized easily.

Galena

Galena has the formulae PbS. It has a relative hardness of 3. It is virtually the only source of lead and an important ore of silver. Its a very common metallic mineral. When found in veins that show a connection to igneous rocks, it is frequently found with silver minerals. Galena is also found in limestones either as veins or as a replacement deposit.

Garnet

Garnet has the formulae A3B2(SiO4)3. It has a relative hardness of 8. It is a widely distributed group with several minerals. Found in both metamorphic and igneous rocks. Its chief use is as an inexpensive gem stone. Much is used as an abrasive materal.

Garnierite

Garnierite has the formulae (Ni,Mg)6Si4O10(OH)8. It has a relative hardness of 4. It is an ore of nickel. It's probably formed as an alteration of nickel bearing peridotites. Has a nice apple green colour.

Glauberite

Glauberite has the formulae Na2Ca(SO4)2. It has a relative hardness of 3. It has a bitter salty taste; dissolves slowly in water. Is a sedimentary mineral formed by the evaporation of saline water. Slowly alters to gypsum when exposed to air.

Glauconite

Glauconite has the formulae (K,Na)(Al,Fe,Mg)2(Al,Si)4O10(OH)2 It has a relative hardness of 2. It is of marine origin and found in sedimentary deposits of various kinds. Similar to a mineral called celadonite. Used in the textile, sugar, and brewing industries; as a colouring agent and in the manufacture of fertilizers.

Glaucophane

Glaucophane has the formulae Na2(Mg,Fe)3Al2Si8O22(OH)2. It has a relative hardness of 7. It often has a blue colour. A sodium rich rock forming mineral which, like other amphiboles, is poor in silica. Of interest to petrologists in helping to define the metamorphic conditions which formed the surrounding rock.

Gneiss

Gneiss refers to a coarsely foliated (layered) metamorphic rock.

Goethite

Goethite has the formulae FeO(OH). It has a relative hardness of 6. It is an ore of iron and a common mineral. Usually formed as a weathering product of iron bearing minerals. The term "limonite" is commonly used for earthy yellow and brown goethite.

Gold

Gold has the formulae Au. It has a relative hardness of 3. It is a rare element but occurs in nature in widely distributed small amounts. The main source of gold is in gold-quartz veins where gold was deposited from mineral bearing solutions. When the veins weather, the gold is separated from the quartz and mechanically settles on the stream floor as a placer deposit.

Granite

Granite is a plutonic igneous rock containing a high proportion of silica.

Graphite

Graphite has the formulae C. It has a relative hardness of 2. It is pure carbon and often confused with the heavier molybdenite. Formed from organic materials or by the presence of hydrocarbons in a metamorphic region. Used in the manufacture of crucibles, as a lubricant when mixed with oils, as 'lead' for pencils when mixed with clay. Feels greasy.

Greasy

Greasy refers to a luster of a mineral which appears to be covered with thin coat of oil.

Greenockite

Greenockite has the formulae CdS. It has a relative hardness of 4. It is the most common mineral containing cadmium but found in few places and usually as an earthy coating on zinc ores. The largest use of cadmium is for electroplating other metals to form chemical resistant coatings.

Gypsum

Gypsum has the formulae CaSO4ù2H2O. It has a relative hardness of 2. It is a common mineral distributed in sedimentary rocks, often as thick beds. Usually found under beds of rock salt as it's one of the first minerals to crystallize from evaporated salt waters. Used in the production of plaster of Paris.

Habit

Habit refers to the physical form of a crystal. It's determined by the shape and relative proportions of the crystal faces.

Haematite

Haematite is an iron ore.

Halides

Halides refers to a group of minerals that are mostly compounds of halogen elements (bromine, chlorine, flourine, iodine). Ex: halite, flourite.

Halite

Halite has the formulae NaCl. It has a relative hardness of 3. It is common salt. Tastes salty and exhibits lusterless cubic crystals.

Hardness

Hardness refers to hardness is the resistance of a smooth surface to scratching. It's determined by the binding force of atoms within the crystal structure. Moh's scale of hardness: 1)talc 2)gypsum 3)calcite 4)flourite 5)apatite 6)orthoclase 7)quartz 8)topaz 9)corundum 10)diamond.

Harmotome

Harmotome has the formulae (Ba,K)(Al,Si)2Si6O16ù6H20. It has a relative hardness of 5. It occurs mostly in volcanic rocks, especially basalt.

Hausmannite

Hausmannite has the formulae Mn2O4 It has a relative hardness of 6. It is an excellent ore of manganese.

Hauyne

Hauyne has the formulae (Na,Ca)4-8(Al6Si6)O24(SO4,S)1-2. It has a relative hardness of 6. It is of interest to collectors. Occurs in igneous and volcanic rocks.

Hematite

Hematite has the formulae Fe2O3. It has a relative hardness of 7. It is the most abundant and important ore or iron. Has been found in enormous deposits in the United States and elsewhere. Many samples are soft as the hematite is sedimentary or weathered iron oxide and the true hardness is not being measured.

Hemimorphite

Hemimorphite has the formulae Zn4Si2O7(OH)2ùH2O. It has a relative hardness of 5. It is an ore of zinc. Found in the oxidized regions of zinc deposits.

Heulandite

Heulandite has the formulae (Na,Ca)4-6Al6(Al,Si)4Si26O72ù24H2O. It has a relative hardness of 4. It is found in the cavities of basic igneous rocks and often associated with calcite.

Hexagonal

Hexagonal refers to a six sided crystal with hexagonal bases. An unsharpened pencil is a basic example.

Horn Silver

Horn Silver is a native chloride of silver, so called because when fused it assumes a horny appearance.

Hornblende

Hornblende has the formulae (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH)2 It has a relative hardness of 6. It is a common member of the amphibole group. Told from pyroxene by cleavage. Found in igneous and metamorphic rocks.

Hydrothermal

Hydrothermal refers to the alteration of minerals or rocks by super-heated mineral rich fluids, usually water, within a crystallizing magma.

Hydrozincite

Hydrozincite has the formulae Zn5(CO3)2(OH)6. It has a relative hardness of 3. It is found mainly in deposits associated with smithsonite and occurs as a result of the oxidation of zinc bearing minerals. A major ore of zinc if found in economic quantities.

Ilmenite

Ilmenite has the formulae FeTiO3. It has a relative hardness of 6. It has weak magnetism. The major ore of titanium and a common accessory mineral in plutonic rocks. Also in metamorphic rocks. Occurs concentrated in black sands. Associated with magnetite.

Intermediate rock

Intermediate rock refers to an igneous rock that is transitional between acidic and basic rocks. Have a silica content between 54-65%.

Iron

Iron has the formulae Fe. It has a relative hardness of 5. It is is recovered primarily from iron bearing minerals. Iron is recognizable by the oxide coating on its surface.

Isometric

Isometric refers to cubic. Three axis, all the same length and at right angles to each other.

Jade

Jade is a group of glassy silicate minerals including jadetite and nephrite.

Jadeite

Jadeite has the formulae Na(Al,Fe+3)Si2O6. It has a relative hardness of 7. It is long prized in the Orient where its been used to make beautiful ornaments. Occurs in large masses in serpentine. Transparent and translucent varieties are called jade.

Jasper

Jasper has the formulae SiO2. It has a relative hardness of 7. It is a form of quartz usually coloured red from inclusions of hematite.

Jet

Jet is a soft black mineral.

Kaolinite

Kaolinite has the formulae Al2Si2O5(OH)4. It has a relative hardness of 3. It has a crumbly habit. One of the common members of the group called clay. Derived from the decomposition of feldspars, particulary aluminum silicates. One of the most important of the natural industrial substances, it is used for bricks, ceramics, and many other applications.

Kernite

Kernite has the formulae Na2B4O7ù4H2O. It has a relative hardness of 3. It is a major ore of boron. Formed in playa lakes with the boron supplied by thermal springs passing through the underlying volcanic rock.

Kimberlite

Kimberlite is an igneous rock containing very little silica.

Kyanite

Kyanite has the formulae Al2SiO5. It has a relative hardness of 7. It has a different hardness in two directions. An accessory mineral in gneiss and mica schist. It often found with garnet and corundum. Used in the production of refractory porcelains.

Labradorite

Labradorite has the formulae (Na,Ca)AlSi3O8. It has a relative hardness of 6. It is one of the plagioclase feldspars, also known as soda-lime feldspars. Others in the grouping are: albite, oligoclase, andesine, bytownite, and anorthite. Labradorite often has a beautiful display of colours. The name is derived from the locality of Labrador.

Lamellar

Lamellar refers to composed of thin layers, scales, or plates

Lapis lazuli

Lapis lazuli is a blue mineral used in the manufacture of ultramarine pigment.

Laumontite

Laumontite has the formulae Ca(Al2Si4)O12ù4H2O. It has a relative hardness of 4. It shows a powdery white surface. A form of anaclime (or analcite). Characterized by the fact that it is monoclinic.

Lazulite

Lazulite has the formulae MgAl2(PO4)2(OH)2. It has a relative hardness of 6. It is a rare mineral and a minor gem stone. Usually found in quartzites associated with kyanite, andalusite, corundum and rutile. Name derived from the Arabic word for 'heaven' in regard to the mineral's colour.

Lazurite

Lazurite has the formulae (Na,Ca)8(Al,Si)12O24(S,SO4). It has a relative hardness of 5. It is usually shows a deep blue colour. The greenish variety is called lapis lazuli and is very rare. Found in metamorphic limestones associated with calcite and pyrite.

Lenticular

Lenticular refers to have a lens-like shape.

Lepidolite

Lepidolite has the formulae K(Li,Al)3(Si,Al)4O10(F,OH)2. It has a relative hardness of 4. It is a relatively rare mineral found in pegmatic dikes and usually associated with lithium bearing minerals such as pink and green tourmaline. Often found intergrown with muscovite. Used as a source of lithium and it's used in the manufacture of heat resistant glass.

Leucite

Leucite has the formulae KAlSi2O6. It has a relative hardness of 6. It is a rather rare mineral occuring only in igneous rocks and usually in recent lavas. Found in rocks where the amount of silica in the magma was not sufficient to form feldspar. It is not found, therefore, in rocks that contain quartz. From the Greek word for 'white'.

Lime

Lime is the common name of calcium oxide.

Limestone

Limestone is a sedimentary rock composed of calcium carbonate.

Limonite

Limonite is an iron ore found in bog deposits. It has a relative hardness of 5.5.

Luster

Luster refers to the general look of a mineral in reflected light. Minerals are divided into two types: metallic and non-metallic. There's no clear dividing line between the two. In general, non-metallic minerals will transmit light through a thin edge, are light coloured, and will have a light or colourless streak. Non-metallic minerals are further described as: vitreous, resinous, pearly, greasy, silky, adamantine.

Magma

Magma refers to molten rock beneath the earth's crust. It solidifies to form igneous rocks.

Magnesite

Magnesite has the formulae MgCo3. It has a relative hardness of 4. It has been used as an ore of metallic magnesium but the primary source of magnesium is sea water. Is a source of magnesia for industrial chemicals. Commonly found in veins and masses derived from the alteration of serpentine through the action of waters containing carbonic acid.

Magnetite

Magnetite has the formulae Fe3O4. It has a relative hardness of 7. It is the richest and most important ore of iron. Found as an accessory mineral in most igneous rocks. Highly magnetic.

Malachite

Malachite has the formulae Ci2(CO3)(OH)2. It has a relative hardness of 4. It is a widely distributed copper ore. Found in the oxidized portions of copper veins and is often associated with azurite, cuprite, native copper, iron oxides, and sulfides of copper and iron. Often occurs in copper veins that are found in limestone.

Manganite

Manganite has the formulae MnO(OH). It has a relative hardness of 4. It is strongly magnetic. An ore of manganese but seldom found in commercial quantities. Often found in veins associated with granitic igneous rocks. Alters to pyrolusite. Barite and calcite are frequent associates.

Marble

Marble is metamorphosed limestone.

Marcasite

Marcasite has the formulae FeS2. It has a relative hardness of 7. It often shows a white colour on a fresh surface. Found in iron metallic veins and frequently with lead and zinc ores. Also found in sedimentary rocks. Marcasite most frequently occurs as a replacement deposit in limestone and often in concretions imbedded in clays, marls, and shales.

Margarite

Margarite has the formulae CaAl2(Al2Si2))O10(OH)2. It has a relative hardness of 5. It is a metamorphic mineral associated with staurolite and tourmaline.

Massive

Massive refers to a mineral that does not show any definite external crystal form or consists of poorly defined masses of small crystals.

Mercury

Mercury has the formulae Hg. It has a relative hardness of 0. It is a native metal. Has uses in mining, engineering, and pharmacy.

Mica

Mica refers to a group of silicate minerals having perfect cleavage in one direction and which easily split into thin, elastic, sheets.

Microcrystalline

Microcrystalline refers to a rock in which the crystals are too small to be seen without a microscope.

Microline

Microline has the formulae KAlSi3O8. It has a relative hardness of 7. It has the same composition as orthoclase but distinguished by triclinic twinning (usually requires a microscope). If a feldspar is a deep green it is microline - and sometimes called 'amazon stone'. Told from plagioclase by lack of striations.

Millerite

Millerite has the formulae NiS. It has a relative hardness of 4. It is the richest ore of nickel but too scattered to be commercially important. Forms at low temperatures often in cavities and as an altered form of other nickel minerals, or as a crystal inclusion in other minerals.

Mimetite

Mimetite has the formulae Pb5(AsO4)3Cl. It has a relative hardness of 4. It is a minor ore of lead. A relatively rare which occurs in the oxidized portions of lead bearing veins.

Mohs

Mohs is a scale of hardness applied to minerals. It ranges from 1 for talc to diamond at 10.

Molybdates

Molybdates refers to a group of minerals in which the molybdate radical (MoO4) is an important constituent. Ex: wulfenite

Molybdenite

Molybdenite has the formulae MoS2. It has a relative hardness of 2. It is the main ore of molybdenum. Resembles graphite but has a higher specific gravity and a slight blue tint.

Monazite

Monazite has the formulae (Ca,La,Nd,Th)PO4. It has a relative hardness of 6. It is the chief ore of thorium and cerium. Thorium is a radioactive element. It is concentrated in sands due to its durability and high specific gravity. Associated with other heavy minerals such as magnetite, rutile, and zircon.

Monoclinic

Monoclinic refers to a crystal with six faces and three axes of unequal length. Two axes are at right angles to each other and the third is inclined to the plane of the other two. A ream of paper with a long edge sloped at an angle is an example.

Mud

Mud is a mixture of clay, sand and organic matter.

Muscovite

Muscovite has the formulae KAl2(AlSi3)O10(OH)2. It has a relative hardness of 3. It has extremely perfect cleavage and thin flakes are flexible. Very common. Used for electrical and heat insulation.

Natrolite

Natrolite has the formulae Na2(Al2Si3)O10ù2H2O. It has a relative hardness of 6. It is of interest to collectors. Found lining cavities in basalts and other lavas. Associated with calcite and zeolites.

Nephiline

Nephiline has the formulae (Na,K)AlSiO4. It has a relative hardness of 6. It is confined almost exclusively to the zinc deposits at Franklin, NJ. Associated with franklinite and willemite, often in an intimate mixture.

Niccolite

Niccolite has the formulae NiAs. It has a relative hardness of 6. It is a minor ore of nickel and often has a copper-like colour.

Nodular

Nodular refers to appearing as or composed of irregular lumps of rock or a mineral.