Wet Chemical Techniques One technique to analyze the chemistry of a mineral is to dissolve it Water Strong acids bases hydrofluoric acid oxidants fluxes of other material dissolve mineral Analyze the chemical constituents now dissolved in the resulting solution Spectroscopy often using Inductively coupled plasma ICP or flame to ionize the atoms and investigate the effects of on visible light Planck s law E h hc Where is frequency is wavelength h is Planck s constant and c is the speed of light Spectroscopy Exactly how energy is absorbed and reflected transmitted or refracted changes the info and is determined by different techniques sample Transmittance spectroscopy Reflected spectroscopy Raman Spectroscopy Analytical Techniques for Minerals XRD X ray diffraction is one of the most powerful tools for mineral identification structural chemical refinement and size determination we will study it in detail both lecture and lab Microscopy Optical techniques are another very powerful tool for mineral identification identification of physical chemical history of minerals rocks and mineral association which we will also study in detail both lecture and lab Analytical Techniques for Minerals Spectroscopy different methods of studying how different parts of the electromagnetic spectrum of which visible light is a small part are affected by minerals Electron microscopy look at techniques which utilize how electrons shot through a sample of mineral interact with minerals imaging possible to very small sizes Scanned proximity probe microscopy techniques look at forces between probe tip and sample to measure a property height optical absorption magnetism etc More analytical techniques Sychrotron Different techniques many similar to spectroscopic techniques that utilize particles accelerated to very high speeds and energies and how they interact with minerals Magnetic different techniques that utilize the magnetic properties of minerals Size techniques to determine the sizes of different minerals Chemistry isotopes techniques to probe chemical and isotopic signatures in minerals Spectroscopy Exactly how light is absorbed and reflected transmitted or refracted changes the info and is determined by different techniques sample Transmittance spectroscopy Reflected spectroscopy Raman Spectroscopy Light Source Light shining on a sample can come from different places in lab from a light on a plane from a laser array or from earth shining on Mars from a big laser Can tune these to any wavelength or range of wavelengths IR image of Mars Olivine is purple Causes of Absorption Molecular or atomic orbitals absorb light kicks e from stable to excited state Charge transfer or radiation color centers Vibrational processes a bond vibrates at a specific frequency only specific bonds can do absorb IR though IR active Reflectance Spectroscopy Non destructive form of analysis used to see some of the chemistry bonding Spectroscopy is particularly good at detecting water and OH groups in minerals especially in IR Good at differentiating between different clays because it detects OH groups well Raman Spectroscopy Another kind of spectroscopy which looks at a scattering effect and what that tells us about the chemistry oxidation state and relative proportions of different ions M ssbauer Spectroscopy Special effect restricted to specific isotopes of certain elements which causes a very characteristic emission after getting hit with a beam of gamma radiation which is sensitive to the bonding environment of that isotope only 57Co 57Fe 129I 119Sn 121Sb Generally used to study Fe tells us about how Fe is bonded and it s oxidation state Nuclear Magnetic Resonance Spectroscopy NMR NMR is useful for determining shortrange cation ordering in minerals The NMR spectrometer can be tuned to examine the nucleus of mineralogical interest e g aluminosilicates 27Al 29Si 23Na oxides 17O 25Mg etc phosphates 31P hydrous minerals 1H 19F NMR is particularly useful for cations that can not be distinguished by X ray methods such as Si Al ordering in aluminosilicates Electron Microscopy What we can see using visible light is limited at the small end of spatial scales by the wavelength of light hundreds of nanometers To image things smaller than this need to use energy of smaller wavelengths Because energy is inversely proportional to wavelength E hc higher energy particles have smaller wavelengths and can image smaller things e are easy to generate and accelerate faster particle has more energy Electron Microscopy Spectroscopy Interaction of electrons with a sample Secondary e e penetration into a sample Details dependent on mineral composition and accelerating voltage of e beam but for SEM applications SEM what do we get Topography surface picture commonly enhanced by sputtering coating the sample with gold or carbon TEM HRSTEM What do we get See smallest features with this sub nm Morphology size shape arrangement of particles on scale of atomic diameters Crystallographic information from diffracted electrons get arrangement and order of atoms as well as detection of atomic scale defects Compositional information Chemical identity including redox speciation distinguish Fe2 and Fe3 for instance Electron Microprobe Very similar to SEM and TEM in many respects but utilizes thick sections and a set of detectors which measure the emitted X Rays from e bombardment and excitation more accurately than the detectors used in SEM or TEM analyses These detectors are wavelength dispersive spectrometry WDS detectors there are usually an array of 3 5 which record over some range of wavelength much more accurately than the EDX detector available with SEM and TEM instruments Synchrotrons A synchrotron is a ring which uses magnets and electrodes to accelerate x rays or light to nearly the speed of light These extremely bright sources have widened the range of information which we can use traditional spectroscopy diffraction and even microscopy techniques for National Synchrotron Light Source NSLS XANES and EXAFS X ray adsorption near edge spectroscopy and Extended X ray adsorption Fine Structure commonly done with synchrotron radiation because the higher energy X ray yields more precise data X ray techniques which look at the fine details of X ray interactions with minerals Sensitive to oxidation states and specific bonding environments Atomic Force Microscopy AFM Can be done in water or air unlike SEM TEM which requires a vacuum The probe is attached to a