This one is the the AGU… there are numerous other data bases. The use of machine learning has been around for a while with SPECIFIC scientific applications but has become generalized with AI…something that we all know already but being mentioned because it does present both
an opportunity and a threat. The threat is also obvious… there are no ethical guardrails for data mining and selling of personal data… as long as money can be made legally off of data selling, there will be no protection for privacy and personal data. Illegal use of data forces all of us to pay for extra security… what the future will hold is up for grabs as AI advances exponentially.
Thin section visual analysis took hours, counting more than one slide to be representative of a whole rock sample… now it can be done is seconds. However the utility of visual representation is still intact… many papers and presentations have pictures of slides alongside with chemical analysis… the slides are kaleidoscopic in color with polarized light… simple rocks that only have three minerals, like common basalts- plagioclase feldspar (labradorite schiller cabochons, Oregon sunstone, New Mexico bytownite sunstone being gem representatives), fosteritic olivine (peridot), and pyroxene (chrome diopside being the gem example) have their own colors under polarized light that change directionally on a rotating stage…opaque accesssory minerals such as magnetite show up as black grains… showing photomicrographs is a common practice in publications. How useful this is for gem analysis is that it isn’t, it’s just science. it give you the MODAL analysis of a rock for classification by estimating the volume of individual minerals within a whole rock sample… chemical analysis by breaking down the rock into consituent oxides and reconstituting the rock by an algorithm into a set of standardized constiuent minerals based on chemistry, gives you the NORMATIVE analysis or NORM… combining the two give you a better understanding the how the rock was formed. In Hawaii, the main mountain building stage of the islands were made out of voluminous eruptions of thoelilitic basalt… the underlying Hawaiian hotspot mantle plume cause large scale decompression melting at upper levels in the oceanic lithosphere leading to a more “primitive” magma composition. As the islands moved off the hotspot, the volcanoes became senescent. Late stage lavas shifted in composition to Hawaiite…lower degrees of partial melting in deeper crust resulted in alkali and silica enrichment. Technically, the silica content qualifies the rock as being an andesite with 57-60% silica, but the sodium content increased also maintaining a trend towards silica undersaturation… modal analysis shows Hawaiite being mostly andesine plagioclase (50-70% albite feldspar) with smaller amounts of clinopyroxene and accessory olivine…Nomative analysis showed 5% jadeite hidden within the titaniferous augite clinopyroxene…thus refecting the under silica saturated trend… very small volume rejuvenated volcanism after 2 million years extinction of main stage thoelititc eruptions continue the unsaturated trend into basanite and nephelinites. The Na content was high enough to overwhelm available silica to make nepheline instead of plagioclase. Due to the small volume of undersaturated magma, not enough was present to make for ore or gem deposits that are often associated with undersaturated rocks… However on continental or subduction zone crust, large volume undersaturated magmas can pool to form nepheline syenites and even more undersaturated rocks… these rocks can host ores and gem minerals… the example of hackmanite presented by PaulB from San Benito county is one of them. Hawaiian rocks do have gemmy high magnesium (fosterite) olivine… but the crystals are too small to cut. Oceanites are up to 40% olivine thoelititic basalt resulting in an attractive rock full of small gemmy peridot crystals within a calcic plagioclase matrix… a good sample can be polished but with some difficulty as the hardness of peridot and and calcic plagioclase vary by 1 and the plagioclase tends to cleave…larger (1cm) titanaugite euhedral crystals can be found free in cinders from late stage alkali basalt eruptions. They make attractive mineral specimens- brownish red with great euhedral crystal faces…translucent at the edges but are not of gem quality, common opal and quartz crystals are rare but created by hydrothermal activity within caldera margins… these have been thoroughly picked over by collectors… the only other specimens are native sulfur from active volcano fumaroles and selenite gypsum roses… the roses were formed from montmorillonite clays leaching out calcium when high sea levels flooded lowland valleys on the older islands, with sulfate being provided by sea water… I have a collection of roses that are invaluable, collected when I was a kid… the site has been paved over for decades by a subdivision. Otherwise nothing of gem or specimen interest in Hawaii…the geologic system is too simple…