Glossary

ammonite An extinct type of shelled cephalopod. It has a multi-chambered, generally coiled shell. The chambers of ammonites are separated by complexly corrugated partitions called septa.

ashlar Masonry consisting of stone cut into rectangular blocks.

bema The raised area of a Byzantine-style church where the altar is located.

brachiopod A marine invertebrate with a shell that superficially resembles that of a clam. The shell consists of two valves that are each bilaterally symmetrical. Unlike the shells of most clams, each valve is not the mirror image of the other.

breccia/brecciated A rock composed of large, angular rock fragments with finer-grained material in between.

brownstone A brown, reddish brown, or red sandstone used for buildings.

bryozoan A small aquatic colonial invertebrate. Forms commonly found as fossils may resemble small twigs.

calcareous Material composed at least partially of calcium carbonate.

calcite A generally light-colored mineral composed of calcium carbonate. Calcite is fairly soft and effervesces (bubbles) in weak acids. It is the principal mineral in limestone and many marbles.

calcium carbonate The chemical compound CaCO3. A common natural form is the mineral calcite.

carbonate Material, such as limestone, composed of oxides of calcium and carbon.

cephalopod A member of a group of marine invertebrates that includes octopuses, squids, and their relatives (both modern and extinct), including shell-bearing forms, such as the pearly nautilus. chancel The part of a church in which the main or only altar is found.

clast A fragment of a rock formed by the breaking up of a larger body of rock. Clasts are often recemented together to form a breccia.

coarsely crystalline A term used to describe a rock in which the individual crystals are larger than the grains of table sugar.

colonial Said of animals that live together as an interconnected unit.

coral A marine invertebrate with a soft body and a hard external structure composed of calcium carbonate. Corals live attached to the seafloor, especially in shallow, tropical seas. Some corals live as separate individuals, others are colonial and form extensive reefs.

coursed Stone set in layers, usually horizontally and usually containing stone blocks of more or less equal height. The layers are known as courses.

cross-stratification The layering of sediment that is inclined at an angle to the horizontal.

Devonian Period A mid-Paleozoic period of geologic time. It began about 408 million years ago and lasted until about 360 million years ago.

dolomite A light-colored mineral composed of calcium and magnesium carbonate, (CaMg)CO3. It is fairly soft and dissolves in weak acids, but effervesces (bubbles) less than calcite. It is a common mineral in some limestones and in many marbles. The term is also used for a rock dominated by the mineral dolomite as an alternative to the term dolostone.

dolomitic Used to describe a rock that contains dolomite.

dolostone A rock composed primarily of the mineral dolomite.

drove work A chiseled surface consisting of more or less parallel markings.

feldspar The general name given to any of a group of common rock-forming aluminum silicate minerals that contain the elements potassium, sodium, calcium, or some combination of these. There are two major divisions: plagioclase feldspars and potassium feldspars.

field stone Rough, generally elongate, but in some cases rounded, stones that may be found on the surface in fields and that are used for building stone.

foraminiferan A type of single-celled organism with a hard supporting structure consisting of one to many chambers.

formation A particular body of rock or sequence of rock strata. It is identified by its composition and texture and its position relative to other rock units. Formal formation names consist of two parts: the name of a locality and either the word formation or the name of a type of rock (e.g., sandstone, shale).

fossil Any preserved remains or trace of prehistoric organisms.

fossiliferous Containing fossils.

freestone A fine- or medium-grained stone, typically a sandstone or limestone, that can be cut easily in any direction and that will not split in any particular direction.

fusulinid A type of foraminiferan, usually resembling a rice grain.

gneiss A banded metamorphic rock. The principal minerals in gneiss are usually feldspar, quartz, and mica.

granite A light-colored, coarsely crystalline plutonic rock that consists primarily of potassium feldspars, plagioclase feldspars, and quartz. Granite also may contain mica and other minerals. Builders and architects use this term in a broader sense to indicate any very hard crystalline rock used for building purposes.

granodiorite A coarsely crystalline, igneous rock intermediate in color and composition between granite and gabbro.

horn coral A solitary coral having a cup or hornlike shape. They are common in many Paleozoic limestones.

hornblende A dark green to black silicate mineral containing iron and magnesium; in rock, hornblende is generally distinguished from biotite by the elongate shape of its crystals compared to the flat crystals of biotite.

iconstasis A screen, typically with columns and containing icons, that separates the nave and the sanctuary of an Orthodox or eastern rite church.

igneous A rock that crystallized from hot, fluid rock material either below or at the earth's surface. Igneous rocks consist of interlocking mineral crystals.

limestone A sedimentary rock composed predominantly of the mineral calcite. Many of the rocks called "marbles" by builders and architects are actually limestones.

marble A rock resulting from the metamorphism of limestone or dolomite. Builders and architects use this term in a broader sense to denote any stone, typically composed of calcite or dolomite, that is capable of being polished.

marbleized Made to resemble marble. Marbleizing is commonly done by use of paints and varnishes.

metamorphic A rock derived from pre-existing rock as the result of metamorphism.

metamorphism The collective name for all of the various processes that alter pre-existing rock buried within the earth. The changes result from heat, from the pressure of overlying rock, from the pressures related to mountain-building activities, or some combination of these. Alterations that may occur in the pre-existing rock include recrystalization of minerals, formation of new minerals, and rearrangement of crystals or other particles in the rock.

mica A group of common rock-forming minerals that have a flat shape and cleave easily into thin layers or sheets. One common mica is biotite.

migmatite A rock containing both igneous and metamorphic minerals. Such rocks are often banded.

Mississippian Period A late Paleozoic period of geologic time. It began about 360 million years ago and lasted until about 320 million years ago.

narthex The vestibule of a church, often set apart from the nave by a set of doors.

nave The main, middle part of a church or similar structure. The nave may be flanked by aisles laterally and by the chancel and narthex axially.

orthocerid A type of extinct cephalopod, often bearing a straight, cone-shaped shell.

orthoclase A common rock-forming potassium feldspar ranging in color from white to red.

Paleozoic Era The large division of geologic time between the Precambrian and Mesozoic Eras. It began about 570 million years ago and lasted until about 245 million years ago.

Pennsylvanian Period A late Paleozoic period of geologic time. It began about 320 million years ago and lasted until about 286 million years ago.

pier A solid, vertical, square-edged masonry support.

pilaster A vertical element projecting from a wall, resembling a column, but rectangular in shape.

pitched A type of stone dressing in which the edges are cut back at a constant distance to create a framelike effect for rock-faced stone blocks. This type of dressing was originally done by hand with a pitching chisel.

plagioclase feldspar A common rock-forming silicate mineral ranging in color from white to gray.

plutonic An igneous rock, or relating to igneous rock, that crystallized below the surface of the earth. The crystals in a plutonic rock are the size of grains of sugar or larger.

potassium feldspar A common rock-forming silicate mineral characteristically ranging in color from white to pink and red, but which may be blue, gray, or green.

Precambrian All geologic time from the formation of the earth, about 4.6 billion years ago, to the beginning of the Paleozoic Era, about 570 million years ago.

pyrite A gold-colored mineral composed of iron sulfide. It is informally known as "fool's gold."

quartz A common glassy, clear to gray rock-forming mineral composed of silica.

quoin Stone blocks at the corner of a building that differ from the other materials used for that building. Typically quoins are rectangular blocks that are laid so that, when seen from one side, blocks with exposed sides alternate with blocks with exposed ends.

random ashlar A pattern of ashlar masonry in which rectangular slabs, usually cut to two or more sizes, are set with sides of the slabs oriented either horizontally or vertically, but in an offset pattern.

random coursed A pattern of stonework in which stone blocks of varying heights are laid in layers.

rock faced A rough type of facing, resembling a natural surface, used for the exposed side of blocks of building stone.

rock unit name The name given to a body of rock, such as a formation, at the time of its first formal geologic description.

rood screen A screen, often of wood and including a crucifix, that separates the nave from the sanctuary portion of a church.

rubble Irregularly shaped pieces of stone, typically used for rough construction. Field stones are often used for rubble.

sandstone A sedimentary rock composed of sand-sized grains (between 1/16 and 2 mm in diameter), held together by mineral cement.

sediment Matter deposited by water or wind.

septa Internal partitions within the shell or skeleton of various types of animals, for instance, within the shells of ammonites.

serpentine A typically green mineral, rich in iron and magnesium, found in some metamorphic rocks, such as Verde Antique.

serpentinite A rock consisting primarily of serpentine.

silica Silicon dioxide (SiO2) a rather hard material common as cement in sandstones. Chert, jasper, and quartz are made of silica.

silicate mineral A mineral containing silicon and oxygen as major constituents.

slate A rock derived from the metamorphism of shale. Slate is harder and more durable than shale, but breaks easily into thin layers.

stylolites Natural, irregular seams in limestone that formed where the rock was sutured back together after portions of the limestone dissolved away. Limestone is easily dissolved by weak acids. The dark color of stylolites is due to a concentration of insoluble materials that remained behind.

terra-cotta A baked clay used to make tiles, panels for building facing, and statuary.

terrazzo Flooring composed of stone chips set in a cement matrix.

tetrapod Four-legged stand or small table used in Byzantine-style churches.

trace fossil A footprint, trackway, burrow, or other indirect evidence of a prehistoric animal. Trace fossils are distinguished from body fossils.

tracery Ornamental work, commonly made of stone, surrounding and as part of a window.

trade name A manufacturer's name for a product, such as a building stone. The names Amherst stone, Indiana limestone, and Sunset Red granite are examples of trade names.

travertine Freshwater limestone deposited by springs, commonly with the help of bacterial activity.

vein/veining Any type of linear feature that appears to cross through a building stone.

vug A rounded, often spherical, cavity in a rock, commonly filled in part by crystals.

wainscoting The lining of an inside wall, commonly the lower three feet or so. This term is also used to refer to the material used for the lining.

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