50.8 MB (5.5 MB compressed)
5167 x 3438 pixels
43.7 x 29.2 cm ⏐ 17.2 x 11.5 in (300dpi)
TURTLE ROCK SCIENTIFIC / SCIENCE SOURCE / SCIENCE PHOTO LIBRARY TURTLE ROCK SCIENTIFIC / SCIENCE SOURCE / SCIENCE PHOTO LIBRARY
Gypsum streak test. The streak test is used to determine the colour of a mineral in powdered form. It is done by scraping a specimen across a piece of unglazed porcelain known as a streak plate. Gypsum has a white streak. It is a soft mineral composed of calcium sulphate dehydrate (CaSO4 2H2O). Gypsum is defined to have hardness of 2 in the Mohs scale.
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