The Geology of Mount Blue State Park

Glossary of Geologic Terms

Actinolite - a prismatic mineral, typically dark green, containing calcium, iron, magnesium, silicon, oxygen, and hydrogen; commonly found in calc-silicate granulite.

Apatite - a mineral, typically light green, containing calcium, phosphorus, oxygen, and fluorine; commonly found in pegmatites.

Bed - the smallest subdivision in a stratified series of rocks, marked by a more or less well-developed plane, which separates it from adjacent beds above and below.

Bedding - a collective term signifying the existence of beds.

Bedrock - the solid rock that is part of the crust of the earth, commonly overlain by soil, gravel, etc.

Beryl - a mineral, typically pale blue-green, containing beryllium, aluminum, silicon, and oxygen; found in a number of pegmatites.

Biotite - a platy mineral, typically dark brown, containing potassium, aluminum, iron, magnesium, silicon, oxygen, and hydrogen; one of the mica minerals.

Boulder - a fragment of rock, not attached to bedrock, and larger than 10 inches in diameter.

Calcareous - containing calcium carbonate.

Calcite - a mineral, typically white, containing calcium, carbon, and oxygen; the most common form of calcium carbonate.

Calc-silicate - pertaining to a rock or mineral that is predominantly composed of calcium, silicon, and oxygen.

Clay - two implications may be understood: (1) material of very fine particle size, with the individual grains less than 0.002 inch in diameter; (2) a material composed of minerals that are essentially composed of aluminum, silicon, oxygen, and hydrogen.

Coarse-grained - of large particle size.

Crystal - a polyhedral form, bounded by plane surfaces which are the outward expression of the regular arrangement of atoms which make up a mineral.

Dike - a tabular body, typically of igneous rock, which cuts across the structure of another older rock.

Diopside - a mineral, typically light green, containing calcium, magnesium, iron, silicon, and oxygen; commonly found in calc-silicate granulite.

Dip - the angle at which a planar feature, such as bedding or schistosity, is inclined from the horizontal.

Drift - any rock material transported and deposited by a glacier.

Erratic - any rock material that had been transported prior to being deposited, and thus not merely eroded out of the bedrock immediately beneath it.

Feldspar - one of the most common minerals; white, tan, buff, even pink or greenish; typically not showing a crystal form; containing potassium, sodium, calcium, aluminum, silicon, and oxygen.

Fine-grained - of small particle size

Fold - a bend or flexure in some originally planar feature, such as bedding.

Garnet - a near spherical mineral, typically pink to purplish-red, containing iron, aluminum, silicon, oxygen and commonly other components.

Glacier - a thick body of ice originating from compaction of large amounts of snow, showing evidence of movement.

Grain - the particles of discrete minerals which comprise a rock or sediment.

Granite - a particular type of igneous rock, composed essentially of the minerals quartz and potassium-rich feldspar; commonly a general term for any igneous rock containing quartz and feldspar.

Granodiorite - a particular type of igneous rock, composed essentially of the minerals quartz and sodium-rich feldspar.

Granulite - a term commonly used to indicate a metamorphic rock that does not possess a well-developed schistosity.

Gravel - a mixture of sand and pebbles.

Igneous - pertaining to a rock that has crystallized out of a melt.

Joint - a fracture which interrupts the physical continuity of a rock mass.

Joint set - a group of more or less parallel joints.

Limestone - a sedimentary rock composed chiefly of calcium carbonate.

Magma - a naturally occurring subterranean mobile mass of molten rock.

Marble - a metamorphosed limestone.

Metamorphism - the process of change of the texture and mineral content of a rock, caused by subjection of the rock to temperatures and pressures other than those under which it was originally formed.

Mica - one of a number of platy minerals, of which the most common examples in the park are muscovite and biotite.

Micaceous - containing mica.

Mineral - a naturally occurring inorganic crystalline substance.

Mud - a common term for a mixture of clay and water.

Muscovite - a platy mineral, typically colorless or slightly greenish-yellow; containing potassium, aluminum, silicon, oxygen, and hydrogen; one of the mica minerals.

Orogeny - the process of mountain building.

Outcrop - that part of bedrock that is exposed at the surface of the earth.

Pebble - a particle of rock, the dimensions of which range between 1/10 inch and 2 ½ inch in diameter.

Pegmatite - igneous rock of coarse-grain size, typically found in bodies of smaller size than the main bodies of igneous rock.

Plunge - the angle made by a linear feature, such as an axis of a fold, with the horizontal plane.

Quartz - one of the most common minerals, typically clear or slightly milky or smoky, containing silicon and oxygen.

Rock - any naturally formed aggregate or mass of mineral matter, typically consolidated and coherent.

Sand - particles of rock or mineral grains, the dimensions of which range between 0.002 inch and 1/10 inch in diameter.

Sandstone - a sedimentary rock composed of sand-sized particles. Typically quartz is the most abundant constituent.

Schist - a metamorphic rock characterized by parallel orientation of platy minerals, such as mica.

Schistosity - the prominent foliation in schist produced by parallel orientation of platy materials.

Sediment - a descriptive term for particles that had settled down from suspension in water.

Sedimentary - pertaining to a rock that had formed through consolidation of sediment.

Shale - a rock composed of consolidated mud.

Sill - a tabular body, typically of igneous rock, which is parallel to the bedding of the rock into which it had been intruded.

Sillimanite - a needle-like mineral, typically colorless, containing aluminum, silicon, and oxygen.

Strike - the direction of the intersection of an inclined plane, such as bedding or schistosity, with the horizontal plane.

Till - common term for unstratified drift.

Tourmaline - a mineral of long, thin form; typically black, but sometimes pink, green, or yellow; containing boron, aluminum, silicon, oxygen, and many other elements; commonly found in pegmatites.

Vein - tapered bodies of minerals which formed from melts or solutions.

Introduction Geologic History Objects of Interest Glossary Geologic Map (pdf)

Last updated on January 11, 2008

Contents

The Geology of Mount Blue State Park

Glossary of Geologic Terms