Andy McDonald

Background

I have nearly 20 years of experience working with subsurface data in the oil and gas industry, across technical, software and product-facing roles. My work has included building industry software modules, developing applied machine learning workflows for geoscience problems, and creating technical training material for geoscientists.

I have delivered conference workshops, written long-form technical articles and published open notebooks on Python and subsurface data analysis. I also write independently through Subsurface Syntax, on practical ways of working with geological data.

Why Microscope Lab

The petrographic microscope is where most geologists first meet rocks as minerals rather than lumps, and it is hard to get time on one. Microscope Lab puts a working one in the browser: rotate the stage, cross the polars, slide in the gypsum plate and watch grains go extinct. The interference colours are calculated from the physics, not painted on, so every grain sits where it should on the Michel-Lévy chart.

There are 21 thin sections: seven igneous, metamorphic, siliciclastic and evaporite rocks, and the 14 limestones and dolostones from Carbonate Lab.

Find me

• Website
• Substack
• Medium
• LinkedIn
• YouTube
• GitHub

Photographs

The real photomicrographs in Microscope Lab come from Wikimedia Commons and are used under their licences. Thank you to:

• Darla Sondrol: biotite granite and biotite–hornblende granite (CC0)
• Rockswhisperer: perthite, Strathbogie Granite (CC BY-SA 4.0)
• Strekeisen: tartan-twinned microcline; olivine in basalt (CC BY-SA 4.0)
• Zimbres: plagioclase twinning (CC BY-SA 2.5)
• Tiffany A. Rivera: basalt with olivine phenocrysts (CC BY-SA 4.0)
• uncle.capung (Flickr): basalt with the gypsum plate (CC BY 2.0)
• Julien Leuthold: gabbro from Rum, Scotland (CC BY 3.0)
• Bwooddell: Concord gabbro, PPL and XPL (CC BY-SA 4.0)
• Siim Sepp: gabbro (CC BY-SA 3.0)
• Chd: garnet–mica schist, PPL and XPL (CC BY-SA 3.0)
• Jackdann88: garnet–mica schist, Salangen (CC BY 3.0)
• Michael C. Rygel: quartz arenites, feldspathic arenite, muscovite and the carbonate thin sections (CC BY-SA 3.0 and 4.0)
• Hans-Joachim Engelhardt: rock anhydrite (CC BY-SA 4.0)
• Axel Munnecke: Bahamian ooid grainstone (CC BY-SA 4.0)

Each photograph is credited with a link to its source and licence where it appears. Images under CC BY-SA remain under that licence.

Sources

• Sørensen, B.E. (2013) A revised Michel-Lévy interference colour chart based on first-principles calculations. European Journal of Mineralogy 25, 5–10.
• Wyman, C., Sloan, P.-P. and Shirley, P. (2013) Simple analytic approximations to the CIE XYZ colour matching functions. Journal of Computer Graphics Techniques 2(2).
• Nesse, W.D. (2013) Introduction to Optical Mineralogy, 4th edn. Oxford University Press.
• Mineral optical data (refractive indices, birefringence, pleochroism) cross-checked against Wikipedia mineral pages, Carleton College and MIT OpenCourseWare optical mineralogy notes, and alexstrekeisen.it.