ans25,
Minerals have all sorts of physical properties that go beyond colour and shape that can be used to identify them. I used to live next door to a Canadian geologist of some success who was colour blind. Colour is not always a very reliable property to use. Most minerals have a crystalline structure (crystal system) which is determined by the symmetry of rotation of the point groups which make up its basic elemental structure (see table below). Crystallography is a very complex science and the study of these crystal systems has normally been done by physicists in laboratories using X-ray diffraction techniques and complex computer modelling. Spodumene is in the monoclinic crystal system and quartz for example is trigonal.
Knowing the crystal system is only the start to trying to identify minerals as one crystal system can create minerals of different forms and habits. Take quartz for example which has about 40 different crystallographic forms in nature. Even though quartz has this many forms it's usually easy for a geologist to identify as the geologists use a combination of the mineral's properties not just its crystal form. Quartz is generally identified in the field using this combination of properties.
- hardness (easily scratches glass, also harder than steel)
- glass-like luster
- poor to indistinct cleavage
- conchoidal fracture in crystals, in massive specimens the fracture often looks irregular to the naked eye, but still conchoidal at high magnification.
But because quartz is a rock forming mineral it can sometimes have irregular grains and geologists would need to employ other methods to identify it. Often geologists will cut thin sections of a mineral and look at it under a microscope or pass light through the thin section, as different minerals transmit (polarise) light in different ways. Geologists can also use a small drop of acid or even a flame in some instances to see how minerals react in the field. Spodumene for example comes from the Greek "spodoumenos", "
reduced to ashes, alluding to the grayish white mass that is formed when the mineral is ignited." Certain compounds of lithium give off a crimson flame which increases to a brilliant silver as the flame burns more strongly. I don't know if you can use a flame on spodumnene, I haven't done that experiment.
Even if all of those techniques fail to identify the spodumene and other Li baring minerals in the rock, modern science has come to the rescue and there are real time contact spectrometers which can answer the question. A contact probe is put up against the crystal grain and the spectrum is read and compared to a computer library of mineral spectra. These probes can differentiate between spodumene and lepidolite and definitely between Li baring mineral and non-lithium baring minerals if all else fails and it's all done in real time.
http://www.mining.com/web/identify-...with-spectral-evolutions-orexpress-and-ez-id/
We have to give the geologists some benefit of the doubt as these rocks are billions of years old, they weren't created yesterday and have been through various phases of deformation and metamorphism so identifying the crystal structure will be harder than if the rock was younger and the crystalline forms were better preserved, nevertheless they had nice and clean diamond core and plenty of time to wash it, examine it and run tests prior to parading it in that announcement and as I said 1% spodumene equates to ~8% of the rock and 2% would equate to ~16% of the rock (if all the Li was in the form of spodumene), so the lithium minerals in such quantity would stand out in one way or another and tests should have been done in my opinion before the cores were shown. Given the current results I'm not even sure this pegmatite falls into the LCT category, I'll need to do more research on that front.
There weren't many high grade results in that list on Friday. The highest Li grade was 430ppm Li which equates to a Li2O grade of ~925ppm or 0.925% Li2O over only 1m.
Most of the results where in the sub 50ppm Li, ie less than 107ppm Li2O or <0.1% Li2O.
If we think about what this means for those core samples, if this lithium was all in the form of spodumene (which we don't know if it was at this point) the lithium baring minerals would have formed about 0.8% or less in most of that core and would have been totally absent in a lot of it because many of the results were under the detection limit of 10ppm Li. ie most of that core didn't contain visible amounts of lithium baring minerals at all. No wonder they were impossible to see, they just weren't there in a lot of the rock.
Why were investors not told that these pegmatites contained virtually no lithium from the start or at least warned that there didn't seem to be strong visual (field) evidence of lithium minerals in those cores, is it really that hard to identify spodumene from the surrounding minerals? In my opinion the company should have told investors what the purpose of assaying the cores was, in the absence of strong field evidence that the cores contained economic grades of lithium minerals. Why didn't they get a spectral probe if they were unsure? Why did they leave it to investors to have to bite the bullet and take their medicine?
Eshmun DYOR IMHO
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