Pennyweight Pennyweight A pennyweight (abbreviated dwt, from denarius weight) is a unit of mass that is equal to 24 grains, of a troy ounce, of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams. In the Middle Ages, a British penny's weight was literally, as well as monetarily, of an ounce and of a pound of sterling silver. At that time, the pound in use was the Tower pound, equal to 7,680 Tower grains (also known as wheat grains). The medieval English pennyweight was thus equal to 32 Tower grains. When Troy weights replaced Tower weights in 1527, the
Presolar grains to a sufficiently high level to measure isotopic abundance ratios within micron-sized grains. Ernst Zinner became the undisputed leader of SIMS applications to microscopic grains, earning him historic acclaim. Presolar grains are the solid matter that was contained in the interstellar gas before the Sun formed. The stardust component can be identified in the laboratory by their abnormal isotopic abundances and consists of refractory minerals which survived the collapse of the solar nebula and the subsequent formation of planetesimals. To meteorite researchers, the term presolar grains has come to mean presolar grains found in meteorites, which consist overwhelmingly of stardust.