Glossary of Terms

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OBSIDIAN: A glassy phase of lava, usually black.

O.C.: On centers, an abbreviation frequently used in dimensioning shop drawings, designating dimensions from the center of one member to the center of the next.

OFFSET: A course or unit that is set in from the course directly under it, the opposite of a projection.

OGEE: A stone molding with a reverse curved edge, concave above, convex below.

ONE-MAN BOULDERS: Rough stone under 150 pounds.

ONYX: A variety of quartz in crystalline form of calcium carbonate. It is characterized by a structure of parallel bands each differing in color or in the degree of translucency.

ONYX MARBLE: A crystalline from, commonly microcrystalline, of calcium carbonate deposited usually from cold water solutions. It is generally translucent and shows characteristic layering. Commercially, onyx is considered a marble because it can be polished.

OOLITIC LIMESTONE: Rock consisting mainly of calcite, mostly contains oolites or granular particles (generally tiny fossils or fossil fragments) that have calcium coatings.A calcite-cemented calcareous stone formed of shells and shell fragments, practically non-crystalline in character it is found in massive deposits located almost entirely in Lawrence, Monroe, and Owen counties in Indiana, also in Alabama, Kansas, and Texas.This limestone is characteristically a free stone, without cleavage planes, possessing a remarkable uniformity of composition, texture and structure. It also possesses a high internal elasticity, adapting itself without damage to extreme temperature changes.

OPALIZED: The introduction into a rock of siliceous material in the form of opal, a hydrous silicate.

OPEN-FACED QUARRY: Open, fairly level quarry at or near ground level.

ORGANIC: Designation of any chemical compound containing carbon (some of the simple compounds of carbon, such as carbon dioxide, are frequently classified as inorganic compounds).To date, nearly one million organic compounds have been synthesized or isolated. Many occur in nature; others are produced by chemical synthesis.

OUT-CROP: Rock protruding above or at ground level.

OUT OF WIND: Generally refers to veneer stone.To be out of wind is to have the arris of the stone not in parallel or perpendicular lines; stone which is out of wind has an irregular or rustic appearance.

OVER BURDEN: Waste stone, earth or other quarry material covering useful stone.

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