schist
A strongly foliated crystalline rock, formed by dynamic metamorphism, that can be readily split into thin flakes or slabs due to the well developed parallelism of more than 50% of the minerals present, particularly those of lamellar or elongate prismatic habit, e.g., mica and hornblende. The mineral composition is not an essential factor in its definition unless specif. included in the rock name, e.g., quartz-muscovite schist. Varieties may also be based on general composition, e.g., calc-silicate schist, amphibole schist; or on texture, e.g., spotted schist.

shaft
A vertical or nearly vertical opening of a mine.

sphalerite
An isometric mineral, ZnS , with Zn replaced by Fe with minor Mn, As, and Cd; trimorphous with wurtzite and matraite; perfect dodecahedral cleavage; resinous to adamantine; occurs with galena in veins and irregular replacement in limestone; a source of zinc. Also known as: zinc blende, jack, blackjack, steel jack, false galena, pseudogalena, mock ore, mock lead.

stamp mill
An apparatus, and the building containing it, in which rock is crushed by descending pestles (stamps), operated by water power or steam power. Amalgamation is usually combined with crushing when gold or silver is the metal sought, but copper, tin, and other ores are stamped to prepare them for dressing. The technique is obsolete.

stope
Any excavation in a mine, other than development workings, made for the purpose of extracting ore. The outlines of the orebody determine the outlines of the stope.