Natural Stone Definitions
O
Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
Off Fall
Ogee
A stone molding roughly resembling an “S” shape, with a reverse curved edge: concave above, convex below.
Onyx
A frequently translucent and generally layered, cryptocrystalline calcite with colors in pastel shades, particularly off-white, yellow, tan, and green. Commercial definitions of onyx are given in ASTM C119 as part of the marble group.
Oolitic Limestone
A calcite-cemented calcareous stone formed of shells and shell fragments, practically noncrystalline in character. It is found in massive deposits located almost entirely in Lawrence, Monroe, and Owen Counties, Indiana; and in Alabama, Kansas, and Texas. This limestone is characteristically a freestone, without cleavage planes, possessing a remarkable uniformity of composition, texture, and structure.
Open-faced Quarry
A quarry with relatively large lateral expanse when compared to its depth, in contrast to traditional derrick quarries which had relatively short lateral dimensions and great depths.
OSHA
The acronym for Occupational Safety and Health Administration.
Outcrop
That part of a geologic formation or structure that protrudes above or at ground level.
Outriggers
A temporary support extending from machinery, such as cranes, to provide greater stance width and improve stability when handling loads with extended boom lengths.
Overburden
Stone, earth or other material covering the deposit of stone which must be removed to gain access to stone underneath.
Overhang
The portion of a stone that protrudes past the surface on which it is set.
Oxalic Acid
A relatively strong acid that is used, typically as an additive to other polishing compounds, in the polishing of many marbles and limestones.
