Window
A window is a small ground and polished patch on the outside of a rock, made to show what the inside looks like.
Meteorites are usually covered in a dark fusion crust, and old or weathered ones can be coated in brown rust or desert dust. To see what is underneath without cutting the whole stone, a small area can be ground flat and polished. This little viewing patch is called a window.
Windows are a favourite tool for identification and for dealers showing what a stone contains. Through a window on an ordinary chondrite you may see grey stone with tiny shiny flecks of iron-nickel metal and small round chondrules. On an iron meteorite, a window shows bright metal, and if lightly etched by an expert, part of a crystal pattern. Many Northwest Africa (NWA) stones are sold with a window so buyers can judge the interior while most of the crust stays intact. Earth rocks, by contrast, often show crystals or layers instead, or no metal at all.
A good window is small and placed where it does not spoil the stone's best features. Grinding creates fine dust and needs proper tools and water to keep the dust down, so this is a job for an adult with the right equipment, never for children on their own.
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Level: Explorer Ages 10 and up