Table of Contents

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Note: LOI determines the amount of alteration of the sample, generally, scientists use this to determine the 'freshness' of the ingenious rock being analyzed.  Typically we use unignited powder in the bead preparation as that is what correlate correlates to the certified values.  However it is not always the case. Please speak to the geochemists regarding their preference to of ignited or unignited powders in the bead preparation. There are many standards (both unignited and ignited) available for the geochemists to include in their dataset.

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• Compensated Dual Analytical Balance System (Metler Mettler Toledo balances)
• Drying ovens at 110°C and 60°C
• Muffle furnace
• Sonicating bath

Hard Rock

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Processing

• Splitting room saw
• Buehler grinder/polisher with 70 µm grit diamond grinding wheel
• Sonicator (with small water bath)
• X-Press crusher 
• Spex Shatterbox with tungsten carbide (WC) grinding vessel 
• Spex Mixer Mill with tungsten carbide or alumina canisters 
• Retsch MM400 Mixer Mill

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• 0.172 mM LiBr wetting agent (0.15 mg ultrapure LiBr in 10 mL DI water)
• 400mg of drew sighed lithium metabolite flux (weighed on shore)
• 10% nitric acid (143 mL concentrated nitric acid/L of solution). Caution! always add acid to water.
• Isopropyl alcohol, laboratory grade
• DI Deionized water (18.2 M¿ laboratory 2 MΩ/cm² laboratory water obtained from Chemistry Lab)

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• Beakers
• Glass cleaner
• Tweezers
• Teflon spatula
• X-Press aluminum die
• Core liner pieces
• Delrin plugs1-oz glass bottles
• Sample vials or jars
• Weighing paper, 6 x 6
• Kimwipes

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Rock samples are prepared for ICP analysis using the following procedures on each sample:

1. Cut to size (see Cutting Samples to Size below)
2. Polish (see Polishing Samples on Diamond Wheel below)
3. Clean (see Cleaning Samples below)
4. Dry (see Drying Samples below)
5. Crush (see Crushing Samples in the X-Press in XRD Sample Preparation Hard Rock )
6. Grind (see Grinding Samples in the Shatterbox in XRD Sample Preparation Hard Rock)

Cutting Samples to Size

To cut samples for the X-Press, use the splitting room rock saws (located in the Core Deck) following these guidelines:

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Post-ignition measurements should be taken soon (within an hour) after removing crucibles from the furnace. Failure to do so will disrupt the LOI values. Reweigh the crucible plus the ignited sample to determine how much weight was gained or lost. Follow the same weighing procedure as in Pre-ignition Weighing.

1. Record the final weight in the excel spreadsheet under 'CRUCIBLE + IGN SAMPLE WT'. The spreadsheet will populate the columns 'Post Ignition Loss' and '%LOI'.
2. The formula used to calculate LOI is:

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Copy and paste your spreadsheet into that uploader. Click the 'Edit' button and 'Validate Sheet'. This checks and highlights any errors that need to be fixed. When the spreadsheet comes up clean, click 'Lims' and 'Upload'. The sheet will turn green when the measurements are successfully uploaded. The data is now in LIMS under Chemistry > ICP-AES Solids >Expanded LOI.

Cleaning the Quartz or Alumina Ceramic Crucibles

1. Wash the crucibles with DI water and a small piece of a scouring pad (no soap).
2. Rinse several times with DI water.
3. Place crucibles in a 10% HNO₃ bath for 12 hr. If in urgent need, the quartz crucibles can be soaked a minimum of 2 hours, but extra flux blanks will need to be made and added to batches that use these crucibles.
4. Rinse 3 times with DI water after the acid bath.
5. Dry the quartz crucibles in the oven at a maximum temperature of 60°C. Heat the alumina ceramic crucibles to 800°C in the muffle furnace for 2 hours and allow to cool to room temperature before removing

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Figure 43. Fused glass bead. 

• An analytical procedural blank of Flux is prepared identically to the samples. The 0.4 g of flux (the pre-weighed flux) is fused with 10µL 0.172 mM of LiBr and dissolved. An additional 0.1 g of flux is NOT added to mimic the TDS of the 0.5 g mix of sample + flux because this would provide an inaccurate quantitation of the impurities introduced by the amount of flux used in preparation of the unknowns.

Weighing the Sample

Note: This process is typically done by the chemistry technicians.
Weighing the sample is a critical step. The sample weight should be as close to 100 mg as possible. Inaccuracies in the weight will show up in the analytical results. Print small labels for each sample and place on your small, clear capped vial. On the lid label a sticker with the core, section, and interval. Confirm with scientists what powder you will be using Fresh or Ignited.

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1. Rinse crucibles with DI water.
2. If beads are stuck to the bottom, sonicate with DI water for 30 min or more.
3. Place crucibles in HNO3 10% bath for 12 hr. If you notice any signs of residue, leave in the acid bath for longer. If the crucibles are in urgent need, a minimum cleaning time in the HNO3 10% acid bath is 2 hrs, however, extra flux blanks should be made with these crucibles for analysis to ensure there isn't leftover contamination.
4. Clean a Tupperware container with isopropyl alcohol. Lay down sheets of paper towel and large Kimwipes.
5. Take crucibles out of the acid bath and rinse with DI water 3 times. Place crucible in the container. If the crucibles require polishing, see Polishing the Platinum Crucibles.
6. Cover all crucibles with a large Kimwipe and place in the drying oven in the Chemistry Laboratory. Leave overnight.
7. When dry remove crucibles and bring into the XRD laboratory. Wrap each crucible in a small Kimwipe and and place back in the safe. Lock the safe after all crucibles have been put back.

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