Minerals
Fracture/Cleavage
"How it breaks." -Cleavage: the mineral breaks to form distinct planar surfaces -Fracture: the mineral breaks into rough edges -Conchoidal Fracture: the mineral breaks into smoothly curving surfaces
Monoclinic Structure Characteristics
3 axes uneven in length. 2 axes intersect at a 90° angle while the third axis intersects the others obliquely. This crystal system has the most minerals, with about 1/3.
Orthorhombic Structure Characteristics
Aka "the brick." 3 axes, all varying in length, at right angles to each other.
Inorganic
Almost all minerals are inorganic (not containing any Hydrogen-Carbon bonds). Mineralogists have made exceptions to about 30 organic substances that are considered organic
Crystalline Structure
An ordered atomic arrangement. Opal is an exception
Carbonates
Elements such as Ca or Mg bond to a carbonate group, CO3^2-. Examples include: -Calcite (CaCo3) -Dolomite (CaMg[CO3]2) -Malachite/Azurite
Inosilicates
Chain silcates that make monoclinic crystals. There are 2 varieties, single-chain and double-chain.Pyroxene group has a single-chain structure. Examples include: -Augite While Amphibole group has a double-chain structure: -Hornblende
Streak
Color of the mineral powder
Sulfides
Consist of a metal cation bonded to a sulfide anion (S^2-). Many sulfides have a metallic luster and are considered ore minerals. Examples include: -Galena (PbS) -Pyrite (FeS2) -Chalcopyrite
Sulfates
Consist of a metal cation bonded to the SO4^2- group.Many form by precipitation out of water near or at the earth's surface. Examples include: -Gypsum (CaSO4 · 2 H2O) -Barite
Oxides
Consist of metal cations bonded to oxygen anions. Examples include: -Hematite (Fe2O3) -Magnetite (Fe3O4) -Limonite -Corundum
Native Elements
Consist of pure masses of a single element. Metal atoms are bonded by a metallic bond. Examples include: -Copper (Cu) -Gold (Au) -Silver (Ag) -Mercury (Hg) -Diamond (C) -Sulfur
Silicates
Contain the silica tetrahedron. Most abundant of all mineral groups. The silica tetrahedron form several types of linkages which allow for 7 structural groups: -Nesosilicates -Inosilicates -Phyllosilicates -Tectosilicates -Sorosilicates
Halides
Contains a halogen anion. Examples include: -Halite (NaCl) -Fluorite (CaF2)
Phosphates
Contains a phosphate anion group, PO4. Examples include: -Apatite (Ca3[F3Cl][PO4]3)
Definite Chemical Composition
It is possible to write a chemical formula for a mineral.
Homogenous Solid
Maintains its shape indefinitely. There are 2 exceptions :-Mercury (Hg) -Water
Color
Many minerals vary in color, but some are obvious because of their color. Eg. sulfur
Hardness
Measure of a mineral's relative ability to resist scratching, therefore representing the resistance of bonds in the crystal structure to being broken.
Formed By Geologic Processes
Occurring naturally on or in the earth. Examples include chemical reactions, freezing of molten rock, and precipitation.
Morphing Shapes
Occurs when the edges are "cut off." Seen in fluorite and raw diamonds
Luster
The way a mineral surface scatters light. Minerals are described as metallic or non metallic. Words used to describe minerals with non metallic luster include: -silky -glassy; vitreous -satiny -resinous -pearly -earthy
Biogenic Minerals
This term emphasizes a mineral's origin being from a living organism. Eg. calcite in a clam shell
Hexagonal Crystal System
eg. apatite, niccolite, quartz, zincite, calcite, dolomite, tourmaline, corundum, hematite and more
Monoclinic Crystal System
eg. augite, biotite, gypsum, hornblende, malachite, muscovite, orthoclase, selenite, and many others
Orthorhombic Crystal Structure
eg. azurite, barite, sulfur, olivine, topaz and others
Tetragonal Crystal Structure
eg. cassiterite, chalcopyrite, scheelite, thorite, idocrase, wulfenite, zircon, and others
Isometric Crystal Structure
eg. diamonds, gold, platinum, copper, orgentite, chromite, magnetite, sphalerite, galena, halite, tetrahedrite, garnets, spinel, cuprite, pyrite, bornite, uraninite and others
Triclinic Crystal System
eg. plagioclase, microcline, turquoise and others
Silicate Lab Samples
-Augite (Ino) -Biotite (phyllo) -Chlorite (phyllo) -Hornblende (Ino) -Kaolonite (phyllo) -Muscovite (phyllo) -Olivine (neso) -Orthoclase (tecto) -Plagioclase (tecto) -Quartz (tecto) -Tlac (phyllo) -Tourmaline (tecto) -Topaz (neso) -Garnet (neso) -Beryl
Luster of Specific Minerals
-Galena: metallic -Quartz: vitreous -Pyrite: metallic -Calcite: vitreous -Muscovite: vitreous, pearly -Biotite: virteous, pearly -Hematite: earthy
Mineral Classes
-Oxides -Sulfides -Sulfates -Halides -Carbonates -Native Elements -Phosphates -Silicates
Most Common Elements in the Earth's Crust
-Oxygen (O): 46.6% -Silica (Si): 27.7% -Aluminum (Al): 8.1% -Iron (Fe): 5.0% -Calcium (Ca): 3.6% -Sodium (Na): 2.8% -Potassium (K): 2.6% -Magnesium (Mg): 2.1%
Most Abundant Minerals in the Earth's Crust
-Quartz (SiO2) -Orthoclase (KAlSi3O8)
Mineral ID Useful Properties
-color -streak -fracture/cleavage -specific gravity -hardness -luster -crystal form -magnetism -effervescent
Tetragonal Structure Characteristics
3 axes where the horizontal axes are the same length and the vertical axis (c-axis) is longer or shorter, giving it a stretched or flattened appearance. Axes are at right angles to each other. This crystal system has the fewest minerals
Triclinic Structure Characteristics
3 axes, all of different lengths and none of them intersect at a 90° angle. This structure is the most difficult to recognize. It is the least symmetrical, "everything leans."
Hexagonal Structure Characteristics
4 axes where 3 of them are of equal length and lie at 60° angles from eachother. The horizontal axis is a different length and placed at a 90° angle to the rest.
Rhombahedral Structure Characteristics
A branch of hexagonal crystal structure. Often confused with triclinic crystals, but up close inspection, it exhibits a perfect 6-fold rotation. Minerals include corundum (rubies and sapphires), beryl (emeralds) and tourmaline
Tectosilicates
Framework silica structure. Examples include: -Quartz -Na-Feldspar
Mineral
From text: Naturally occurring solid, formed by geologic processes, that has a crystalline structure a definable chemical composition. Almost all minerals are inorganic
Nesosilicates
Independent tetrahedral groups. The Si tetrahedron don't touch each other, but are separated by other, usually metallic, ions. The most common silicate. Examples iclude: -Olivine -Topaz
Know the crystal systems for the following minerals
Quartz - hexagonal Calcite - hexagonal/rhombohedral Pyrite - isometric Diamond - isometric Fluorite - isometric Barite - orthorhombic Microline (Orthoclase) - monoclinic Corundum - hexagonal/rhombohedral Gypsum/Selenite - monoclinic Halite - isometric
Specific Gravity
Represents the density of a mineral, as represented by the ratio between the weight of a volume of a mineral and the weight of an equal volume of water at 4 degrees celsius
Phyllosilicates
Sheet silica structure. Three O ions of each tetrahedron are shared with adjacent tetrahedra. Perfect cleavage occurs parallel to the plane of the sheet. All micas and clays have this structure.Examples include: -biotite -muscovite -talc -chlorite -kaolonite
Silica tetrahedron
SiO4^4-, four oxygen atoms surround a single silicon atom. It is the building block of silicate minerals
Isometric Crystal Characteristics
The most symmetrical crystal system. Crystal has 3 axes which are at equal in length and at right angles to each other. Contains many recognizable shapes including cubes, octahedrons and morphing shapes.
Crystal Form (or Crystal Habit)
The shape of a single crystal with well formed crystal faces. The habit depends on the internal arrangement of atoms in the crystal
Naturally Occurring
True minerals are formed in nature. Although they can be synthesized in in a lab, in geology, a mineral is a mineral if it occurs naturally.