Glossary and Description of Terms from Identify and Name Search Results

Area (acres)

The calculated area of the digitized polygon. Mines represented as points only are 0.

Coal bed

The stratigraphic unit which the coal was assigned to. For further information consult the Iowa Geological Survey.

Composite grayscale map

If yes, the grayscale map is a mosaic of two or more maps.

County

The county where the centroid of the mine or the point is located.

Data type

The data type used for the mine in the database. The data types are assigned to provide a qualitative description of the accuracy of the location.

• Point location, 1/4 section - mine sites located to an area of one quarter section or less, without known extent. These mines appear as points on the map.
• Point location, w/in section - mine sites located to an area of one section to one quarter section, without known extent. These mines appear as points on the map.
• Surface- surface mines were located and digitized from US Geological Survey topographic maps or aerial photographs. These mines are represented by polygons on the map.
• Surveyed map - mine sites digitized from map prepared by surveying techniques. The maps in this classification included sufficient location information that they could be georeferenced with at least two points or a single point, scale, and orientation. These mines are represented as polygons.
• Surveyed map, poor location - mine sites digitized from map prepared by surveying techniques. These maps included location reference to place them within one section, but did not allow more precise georeferencing. These mines are represented as polygons.
• Unmapped, extent approx. - mine location and extent from from sources other than surveyed mine map. The most common source for these mines were a collection of township maps prepared by the State Mine Inspector in the late 1960's.
• unlocated - mines located by a post office or description, e.g. three miles west of Ottumwa. These mines are not shown on the map, but may be accessed with a name search.

Entrance type

Opening from land surface to the mine used to move coal to surface, miners and equipment to the mine, or for ventilation of the mine. Ventilation and escape entrances were often combined. The hoisting shaft or slope formed part of the ventilation system in nearly all mines.

• Air shaft - Vertical or near vertical opening used for ventilation
• Air slope - Inclined opening used for ventilation
• Escape shaft - vertical opening to provide miners an emergency exit from the mine
• Escape way - inclined opening to provide miners an emergency exit from the mine
• Hoisting shaft - a vertical or near vertical opening used to move coal out of the mine and miners and equipment into and out of the mine. Hoisting power was provided by animals early on especially in small mines and later by steam engines and later still by electrical equipment.
• Slope, adit - an inclined opening used to move coal out of the mine and miners and equipment into and out of the mine. Coal was moved out in small carts running on tracks powered pushed by laborers or pulled by ponies or mules.

Location

For all data types except unlocated, the section, tier and range of the centroid or point location of the mine. For unlocated mines, the information provided in the source is given. These locations were typically a post office.

Map file name

The file name of the scanned document.

Map Id

Unique identifier for the mine map, assigned at the time of database development. Use this identifier to request copies of individual maps.

Map name

The name that appears on the mine map. This name may be distinct from the Site Name and/or Mine Name.

Map size

The size of the original map (in.).

Map scale

The scale of the original map. This was nearly always expressed as inches:feet, e.g. 1 in. = 200 ft. Few maps had scale bars, but the scale could often be verified by measuring known features on the map such as distance between section corners.

Mine name

The name used for the mine during some part of its operating span. In cases where a time period for which the name is relevant could be documented, the period will appear in the Years field.

Mining Method

The pattern of mining used to remove the coal. Diagrams (p. 6 and 7)

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• Room and pillar - alternating rooms (coal removed) and pillars (coal left to support mine roof) worked outward from haulageways. Removed 40 percent or more of the coal if pillars are removed before the active section of the mine is abandoned.
• Longwall - coal mined outward in radiating panels from haulageways. Removed 85 percent or more of the coal.
• Combination - uses both room and pillar and longwall mining methods.

Multiple mines

If yes, the mine map shows more than one mine and may be used as the map for more than one mine site.

Number of maps

Mines were required to submit an updated map every two years after the Office of State Mine Inspectors was organized. For this reason some mines are represented by more than one map. The largest number of maps for a single mine is thirty-one including a number of duplicate maps. The number of maps available here is reflected in the Mine Map Information section of the identify result.

Owner

The name of the mine owner and/or superintendent during the period in the Years field.

Site name

The name assigned to the geographic site of the mine usually derived from the last name used for the mine. This name may be distinct from the Map Name and/or Mine Name.

Site Id

A unique numeric identifier assigned to mine sites. These were assigned sequentially as the sites were added to the coal mine database. The first 1-2 digits are the county number where the mine is located. If no Site Id is shown in the Name search result table, the site could not be located.

Shaft depth

Distance (ft.) from land surface to the bottom of the shaft. This measurment may include the thickness of the coal seam and depth of a sump at the bottom of the shaft.

Years

(Name search results only) The period for which the name (site/map/mine/owner) is applicable

Years of Operation

(Identify results only) The known range of years that mining occurred on the site. If the first or last number is missing then no earliest or latest date of operation could be established. In some cases no date information was available.