Prehistoric Chert Types of the Midwest by Tony DeRegnaucourt and Jeff Grorgiady states: (typing in its entirety)
Origin of Chert's Name: Named after the Harrodsburg formation in which this material outcrops in southern Indiana.
Other Names for same type: Ramp Creek and Alum Creek.
Similar Types or Look-Alikes: Other fossiliferous cherts of the Midwest are very similar including Bisher, Brassfield, some Muldraugh,. and any other oolitic chert.
References: Tomak (1970 & 1981), Basssett (1980), Shaver et al (1970), DeRegnaucourt (1991 and 1992), Justice (1987), Smith (1995) and Tankersley (1989).
Geological Stratigraphy: Harrodsburg Limestone Formation of the Sanders Group, Valmeyeran Series, Mississippian System.
Outcrop Location or Chert Source: Outcrops extensively in Monroe, Lawrence, Jackson, and Brown Counties of Southern Indiana.
Naturally Occurring form of Chert: It occurs as bedded lenticular deposits in its parent limestone matrix. It is often found in tabular chunks in the stream gravels of the outcrop vicinity.
Color: The color is highly variable ranging from almost pure white, to cream, to yellow, tan, brown, dark brown, pink, red, and blueish grey and blue. Heat treatment gives the material many colorful pink and reddish hues. Some material approaches dark brown and even black. The oolitic nature of the chert makes it porous and earthy to chalky in luster. Munsell colors are 10YR 8/6, 10YR 8/2, N8, 10R 5/8 and 5B 5/1.
Texture: The highly fossiliferous nature of this chert makes it porous in appearance with a chalky to earthy luster. Heat treatment gives it a slightly waxier sheen. The oolitic and brecciated fossil structure is its most distinctive feature making this chert easy to identify.
Minerals present: Microcrystalline quartz, dolomite, pyrite, detrital quartz, and chalcedonic quartz-filled cavities and vugs Tankersley (1989).
Fossils: Extremely numerous echinoderm plates, bryozoan colonies, and brachiopods.
Prehistoric Geographic Distribution: This chert is found primarily in south central Indiana. However, it is often found across the Ohio River in north central Kentucky and ranges into central Kentucky over 50 miles into the interior. It is hypothesized that the Harrodsburg formation outcrops somewhere in central Kentucky as well as southern Indiana. An occasional piece of this material makes into east central Indiana and southwestern and west-central Ohio. The most far-flung instance of this material in Ohio is in Shelby County, Ohio near the town of Botkins where a late Paleo and early Archaic component occurs (DeRegnaucourt 1997a) This type is scarce in southwestern Ohio.
Prehistoric Utilization: Harrodsburg was rarely used during Paleo-Indian times. Only three Clovis points are known to the authors to be made of this material (Roger Tucker, personal communications). Usage during the Early Archaic is more common with the occasional Kirk Tradition and Bifurcate Tradition points being made of this type (Smith 1995 and DeRegnaucourt 1991 & 1997a). Middle Archaic usage is limited to the local area of the outcrop. The Late Archaic Period was when Harrodsburg chert reached its zenith in utilization. Many Schershel and Raisch-Smith points were also made of Harrodsburg chert. Woodland Period usage of Harrodsburg chert was practically non-existent and this absent continued into other later prehistoric periods. It appears that after late Archaic Period, the Harrodsburg material and quarries fell into disfavor as apparently other more easily workable sources of chert were available to the prehistoric Indians of the region.
THIS IS THE HARRODSBURG CHERT PLATE 21 FROM THE BOOK
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