The clean, digital interfaces above represent laboratory conditions. I need you to understand that field testing is chaotic. When you are standing in a sorting house in Ndola with poor overhead lighting, sweat on your hands, and a parcel of fifty stones, the textbook rules bend.
The Loupe Deception: Using a 10x loupe requires a steady hand and perfect backlighting. In the field, you will mistake surface abrasions for internal fractures. You will stare at a tiny bubble in a Ural fluid inclusion, waiting for it to move as you tilt the stone. Here is the trick nobody mentions: if the ambient temperature is too low, the fluid inside that microscopic pocket becomes highly viscous. The bubble will not move. You must literally hold the rough stone tight in your closed fist for three minutes to transfer your body heat, lowering the fluid viscosity, before trying the loupe again.
The Dichroscope Glare: Pleochroism is a fantastic indicator, but only if you aren't fighting external reflections. A raw crystal face acts like a jagged mirror. If you don't use immersion fluid (or at least a drop of water in the field) to smooth the optical entry point, the surface glare will trick your eye into seeing color shifts that aren't actually happening inside the crystal lattice.
FTIR Limitations: Even back in the lab, heavy machinery has blind spots. We use Fourier Transform Infrared (FTIR) spectroscopy to detect irradiation treatments. But if a Congolese specimen is heavily fractured or packed with dense hematite, the infrared beam scatters. The machine spits out noise. At that point, you are back to relying entirely on your visual experience and tactile judgment. The machine is a tool, not a savior.