Hello Rich: I am wondering why you are grinding by hand and what you are grinding. Some of the cleaning and prep methods described in this topic are so overly excessive (triple cleaning) and potentially productive of contamination (I would never put a rock or chips to be analyzed in a disc mill, the shearing action can lead to gross contamination compared to the crushing action of a chipmunk) that they inspire me to respond. Have you considered the amount of sub-sample necessary to be representative of the rock you are analyzing? For most common metamorphic and plutonic rocks that amount will be on the order of hundreds of grams. For those rocks we routinely sub-sample (after crushing) with a line splitting method down to 80 grams, which is the maximum amount we like to put in our ring mill. For volcanic rocks with large phenocrysts the amount of representative sub-sample required may also exceed 80 grams, so we line-split those as well. The small amounts of sample one can grind by hand in a mortar and pestle scare me given these considerations. Are you rotary or line splitting to produce the small sub-sample amount that will fit in a mortar and pestle? (I trust you are not coning and quartering, a very imprecise means of sub-sampling). Also, I understand there may well be micrograms of the prior sample adhering to the surface of the pestle or stuck in the pores. But please do the mixing calculation - how much contamination would be required to be detectable by the instrumentation you are employing? That of course depends upon how much sample you add to grind (and pre-grinding some part of your sample is a waste of time, which assumes that even after rigorous cleaning, somehow the media can't be trusted). Don't adopt a far too tedious cleaning procedure unless you are dealing with tiny amounts of material, and you have evaluated the mixing model. For normal rocks those considerations are trivial, with simple and efficient cleaning you can go about your business in confidence. Be practical! What do you gain by using wet sand etc., that you can't get with a rough scrubbing with a Scotchbrite pad and some compressed air? Regards, Rick Richard Conrey Hamilton Analytical Lab Geosciences Dept. Hamilton College 198 College Hill Road Clinton, NY 13323 rmconrey@hamilton.edu > > On Wed, Jan 26, 2022 at 9:38 AM Gaschnig, Richard M via MSA-talk < > msa-talk@minlists.org> wrote: > >> Hi all. For those of you that make powders by hand grinding with a >> mortar/pestle set, how do you go about cleaning the media between samples? >> >> >> >> Dr. Richard (Rich) M. Gaschnig >> >> Assistant Professor >> >> Graduate Coordinator >> >> Department of Environmental, Earth and Atmospheric Sciences >> >> University of Massachusetts Lowell >> >> Lowell, MA 01854 >> >> http://www.richardgaschnig-geology.com >> >> >> _______________________________________________ >> MSA-talk mailing list -- msa-talk@minlists.org >> To unsubscribe send an email to msa-talk-leave@minlists.org >> > > > > _______________________________________________ > MSA-talk mailing list -- msa-talk@minlists.org > To unsubscribe send an email to msa-talk-leave@minlists.org >

Hi Rich I use a bit of a broken glass microscope slide. I always have some used or broke slide in the sharps. I cover it with some weighing paper so it doesn't throw any broken pieces of glass out and then crush it up. I then grind it till everything is smooth. After that I wipe out the powder and clean with acetone. Cheers Lowell Lowell Miyagi Associate Professor University of Utah Geology/Geophysics 115 So. 1460 E. Rm 325 Salt Lake City, Utah 84112-0111 ________________________________ From: Steve Shirey via MSA-talk <msa-talk@minlists.org> Sent: Friday, January 28, 2022 5:06 AM To: Gaschnig, Richard M <Richard_Gaschnig@uml.edu> Cc: msa-talk@minlists.org <msa-talk@minlists.org> Subject: [MSA-talk] Re: cleaning procedures for mortar/pestle Hi Rich- We always clean all our grinding apparatus with bull quartz or single crystal quartz. It's much cleaner than beach or sea sand (no feldspar, monazite, or zircon) for all trace elements. We treat it like you would chips of rock and put it through every step of the process: ceramic jaw crusher, ceramic disk mill, and finally mixer mill, shatterbox, or mortar and pestle. It will add a small amount of silica to a whole rock analysis (<0.5 wt%) but little else. If you have enough sample you can eliminate the silica effect by pregrinding a small aliquot of the rock you are crushing and discard it. Then go immediately to grind the aliquot you will keep of the rock. This step will contaminate the apparatus with the rock you already have and completely eliminate cross contamination or added silica. Afterward go back to the quartz to clean the apparatus. With best regards, Steve On Wed, Jan 26, 2022 at 9:38 AM Gaschnig, Richard M via MSA-talk <msa-talk@minlists.org<mailto:msa-talk@minlists.org>> wrote: Hi all. For those of you that make powders by hand grinding with a mortar/pestle set, how do you go about cleaning the media between samples? Dr. Richard (Rich) M. Gaschnig Assistant Professor Graduate Coordinator Department of Environmental, Earth and Atmospheric Sciences University of Massachusetts Lowell Lowell, MA 01854 http://www.richardgaschnig-geology.com<http://www.richardgaschnig-geology.com/> _______________________________________________ MSA-talk mailing list -- msa-talk@minlists.org<mailto:msa-talk@minlists.org> To unsubscribe send an email to msa-talk-leave@minlists.org<mailto:msa-talk-leave@minlists.org> -- Steven B Shirey , PhD Earth and Planets Laboratory Carnegie Institution for Science Washington, DC 20015 USA www.carnegiescience.edu/stevenbshirey<https://sites.google.com/carnegiescience.edu/stevenbshirey/home> (301) 792-9083 <mailto:sshirey@carnegiescience.edu>sshirey@carnegiescience.edu <mailto:sshirey@carnegiescience.edu> [https://drive.google.com/uc?id=18u3TK81CnDJ-Fwzyrl_nxU6X3UW7S5Mm&export=download]