(click on the large picture for more information in our forum)
Analysing one way... (photo: maurice de graaf).
Analysing other ways:
XRD
x-ray diffractometry (german: RBA-RDA: röntgen beugungs analyse - röntgen diffraktometrie analyse)
What is does: Automated qualitative x-ray analysis. Gives information related to the crystal structure. Diffractograms are mainly used to identify phases (in our case; minerals). XRD yields a diffraction pattern of the crystal lattice. Each diffraction pattern is characteristic (d-spacing, intensity) for a specific structure (besides effects from measuring techniques and preparation). Identification of the mineral by comparision of the measured pattern with the patterns in a database. Distinction between minerals with the same or nearly identical lattice parameters is impossible or problematic. Identification of amorphous minerals is impossible. Distinction between minerals with the same chemistry, but different structure (e.g. Pyrite/Marcasite) is possible. Mixtures of minerals yield in many cases such complex X-ray diffraction patterns that attribution of peaks hence identification becomes very problematic. The same is true for complex mixtures. Some borates e.g. are mixtures of kernite, colemanite and many other species, and those mixtures can give hundreds of peaks, that in part overlap.
Amount of material needed: 1 mm³ or more of pure, clean, non-mixed material, without matrix or other admixtures; but this depends strongly on the camera/goniometer type used. For most routine powder cameras as much as 50 - 100 mg of pure material may be needed in the form of a very fine powder (grain size < 10 µm).
Machine: Siemens D500, now supplied by nonius (bruker-axs)
Where: Dr.Thomas Witzke
Costs: not for sale, only for research purposes (click on the thumbnails to see pictures of analysis ;-)
Machine: ??
Where: Dr.Günter Blaß
Costs: € 12.50
Machine: Rigaku Miniflex
Where: mueller-mineralien.de
Costs: € 21.00
Machines: Nonius KappaCCD Einkristallröntgendiffraktometer, Philips Pulverdiffraktometer, Renishaw M100 MicroRaman Spectrometer System, Polarisationsmikroskop.
Where: Dr.Uwe Kolitsch (work)
Mehr hier: Mineralienatlas.de
Costs: not for sale, only for research purposes.
Machine: ??
Where: The Arkenstone, Dr. Robert Lavinsky
Costs: USD 30.00
Machine: ARL SEMQ electron microprobe, a Cambridge S-250 scanning electron microscope and a modernized G.E. XRD-6 x-ray diffractometer
Where: Bart Cannon Microprobe
Costs: USD ??
Machine: ??
Where: Attard's Minerals, San Diego, California
Costs: USD 40.00
Machine: ??
Where: Jim Murowchick
Costs: USD 20.00
SEM
scanning electron microscopy (german: REM: raster elektronen mikroskopie)
What is does: making 'photo's' (not really photo's, but secondary electron images and/or backscattered electron images...); imaging at a magnification ranging from some 10 x to 300.000 x (and more)... The resolution, which determines in fact the quality of the image can be as good as 1.5 nm for a SEM equipped with a field emission electron gun.
Machine: see EDX
Where: see EDX
Costs: see EDX
EDX
energy dispersive x-ray spectroscopy (german: EDS: energie dispersive rontgenspektroskopie)
What is does: Automated qualitative (which elements are present) and semi-quantitative (ratio between the elements present: the 'amount' of the elements in the probe in relation to the other elements) x-ray elemental analysis. The identification of the mineral is only done indirectly through the chemical composition. Elements with low atomic number (Li, Be, ...) cannot be measured. Distinction between minerals with the same chemistry, but different structure (e.g. Pyrite/Marcasite) is not possible. Problem: decomposition effects of highly hydrated or other instable minerals under the electron beam.
Amount of material needed: If used in combination with a SEM, roughly 1 µm3 and up (material to be analysed must be pure, without any admixtures). Material has NOT to be powdered as for XRD, on the contrary. Analysis can be done "on the spot" in not to rough samples of e.g. 1 x 1 cm, and a height of max. 1 cm or so, depending on the type of SEM on which the EDX is mounted. In principle the analysis and imaging by SEM/EDX is not destructive, but non-conducting samples have to be coated with gold, so that after sample preparation the sample is not enjoyable anymore in a collection.
Machine: ??
Where: Lapis Leserservice
Costs: not for sale; only if Lapis finds it interesting enough to investigate
Machine: Siemens
Where: Dr.Thomas Raber
Costs: between € 10.00 and € 15.00 (it takes between 1 and 3 months)
Machine: ??
Where: Dr.Günter Blaß
Costs: € 12.50 or € 17.50 (when together with XRD)
Machine: ??
Where: Dr.Günther Schnorrer (work) oder Dr.Günther Schnorrer (private)
Costs: € ??.??
Machine: Siemens
Where: excaliburmineral.com
Costs: $ 55.00 excl shipping (incl SEM-image, Xray-spectra, semi-quantitative weight percents, ZAF corrections and a full written report)
Machine: ??
Where: kaygeedee minerals
Costs: $ 5.00 /grain
EPMA/WDX
electron microprobe analyses / wavelength dispersive x-ray analysis
What is does: Automated quantitative (because it works with standards) elemental analysis. A microprobe is an instrument similar to a SEM. This method needs careful preparation (polished section, sputtering of gold or carbon to make the surface conducting). It's much more timeconsuming than EDX... An EPMA is in fact a SEM, with only a higher accelerating voltage, higher primary current density and usually one or more wavelength dispersive spectrometers (WDX) in addition to an EDX. If suitable flat, polished samples are provided (and the necessary standard samples used) a SEM can, nowadays, do the same job as an EPMA, but with less sensitivity and a somewhat higher standard deviation. A WDX compared to an EDX yields X-ray spectra with a much lower background and a higher sensitivity, but they work MUCH slower and therefore the analysis is quite costly. The price of an EPMA system is roughly the double of that of a SEM/EDX system.
Amount of material needed: compare to EDX, but the specimen needs to be perfectly flat (i.e. polished).
Machine: ??
Where: Dr.Günter Blaß
Costs: € ??.??
ICP-MS
inductively coupled plasma mass spectrometry
click here for more information...
See also:
An excellent article written by Dr.Thomas Raber on this subject (with permission of the author)
and
Page 237-246 of the great book by Paul Tambuyser - Mineralen Herkennen