Quartz is a part of almost all geological environments on Earth.
Quartz is the earth's most common mineral. It is a part of most rock -- though it may not be in all metamorphic rock, since that is formed when any given element is exposed to high pressure or heat. Quartz comes in a wide variety of colors and crystalline shapes. When quartz is exposed to sudden, extremely high pressure --- such as from an atom bomb or meteoric impact --- the quartz's lattice structure shifts slightly, and the quartz grains become misaligned. The misalignment causes dark lines, called "shock lamellae" to run through the impacted quartz's sand grains. Quartz that has these shock lamellae is called "shocked quartz."
Instructions
1. Document where the quartz sample came from. Mark the section of your sample you will cut for viewing under the microscope. Cut off a 1.5 x 1.0 x 0.5 inch section of your sample using a masonry saw.
2. Sprinkle 200-grit silicon carbide onto the lapidary wheel. Grind the section using the lapidary until the section feels as though it has stopped giving resistance against the grit --- the sample is as smooth as the 200-grit can make it. Repeat the grinding process using 400-grit and 600-grit silicon carbide, rinsing the sample off with water and drying it before using the 600-grit. Feel the edge of the sample --- though the sample should still be roughly 0.5 inches thick, the edge should be smooth.
3. Place the sample and the glass slide on a hot plate specially made for geological use. Heat the sample and glass slide to 340 degrees.
4. Remove the sample and glass slide from the hot plate. Spread thermoplastic quartz cement (which will not affect the visual integrity of your sample) onto the quartz sample, as you would spread glue from a glue stick. Spread the cement onto a glass slide the same way. Press the cement-covered side of the quartz sample against the glue-covered side of the glass slide.
5. Cut the sample down to roughly 0.125-inch thick using the masonry saw. Sprinkle 600-grit silicon carbide onto the lapidary wheel and grind the sample until it is roughly (1/1000) 0.001 inch or about 30 microns thick (thinner than the width of a strand of human hair), and looks smooth and clear.
6. Place the slide under the petrographic microscope's cross-polarized light, which shines upwards from below and through the quartz sample. Verify that the quartz sample is thin enough by determining if the light shining through it is light yellow to grey and does not contain too many colors. Grind the sample down further, if necessary, and replace it under the microscope's cross-polarized light.
7. Focus the microscope so you can clearly see individual grains of the quartz sand that makes up your sample. Look for dark lines that intersect each other through any of the grains of quartz sand. Find at least two of the dark lines on a single grain of the sand. Search for as many as 9 sets of these dark lines --- called "shock lamellae" --- in just one individual grain. Recognize that if there is at least one set of shock lamellae in the sample, you are looking at a sample of shocked quartz.
Tags: glass slide, quartz sample, dark lines, shock lamellae, your sample, quartz sand, sample glass
