Brucite is the mineral form of magnesium hydroxide named in 1824 by François Sulpice Beudant for its discoverer, American minerologist and chemist Archibald Bruce. Colors vary and may include light blue, milky white, or lemon yellow. It crystals typically have a fibrous body what could be described as a chalky or pearly luster. The structure of the mineral is maintained only weakly, making the it fragile. It is also know for shearing into perfectly flat sheets due to its crystal cleavages laying parallel to their plates.
Brucite is common, but excellent examples are hard to come by. Notable finds include in Wood’s Chrome Mine in Lancaster County, Pennsylvania as well as in Baluchistan, Pakistan. Recently there was a major discovery of brucite yielding beautiful and rare yellow and lemon-yellow specimens, some of which are startlingly and gorgeously transparent. Because the mineral is so fragile it is usually mined by hand
Besides collecting it is used as a source of magnesium and in some flame retardantion applications.
Image Credit: Yellow brucite (4.0 × 3.0 × 2.5 cm) from Killa Saifullah, Balochistan, Pakistan. By Ivar Leidus – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=98529310