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Generally, our products fall into four broad categories with different sizes within each category:

Armor Stone -

Large boulders weighing 2000 lbs or more. The specification for Armor Stone projects generally allow for a range of rock sizes with upper and lower limits of at least 25% by weight, either side of the mean. In other words, if the mean weight of each boulder was 4000 lbs., the upper and lower limits would be 3000 lbs and 5000 lbs respectively. The dimensions for the individual boulders used for Armor Stone generally have a maximum Aspect Ratio of 3 or 3.5 to 1, where the longest dimension is no longer than 3 or 3.5 times the length of the shortest dimension.

The Armor Stone specified for individual projects often include requirements regarding the characteristics of the rock used including minimum density, abrasion resistance, absorption, freeze/thaw, etc. Presence of seams, serious cracks, drill holes, etc. are also often covered in the specification. Gradation tests, inspection of individual rocks, and other quality control methods may additionally be required.

Armor Stone Classes:

Armor Stone is generally custom produced to the individual specification of the particular project. However, In many Chesapeake Materials locations 2 classes or sizes are inventoried for immediate delivery:

Code Size
ARM1-2040 2000 - 4000 lb.
ARM2-2060 2000 - 6000 lb.

Riprap -

A broad term encompassing rock sizes from roughly 2500 lbs. The classes or size ranges of stone within the Riprap category generally have a range of greater than + or - 50% either side of the mean weight. An example of a tight Riprap spec with limits of + or - 50% would be a Mean of 1000 lbs., with upper and lower limits of 500 lbs and 1500 lbs. The range specified by most individual state DOTs for classes of Riprap is generally much greater than + or - 50%, and is sometimes based on physical size rather than weight. As with Armor Stone, very often the dimensions for the individual rocks used for Riprap have a maximum Aspect Ratio of 3 or 3.5 to 1, where the longest dimension is no longer than 3 or 3.5 times the length of the shortest dimension.

Riprap Classes:

Riprap is produced in both custom sizes (gradations) for individual projects, and in standard sizes. The standard sizes inventoried at each of our quarries is usually governed by the standard specifications for riprap as defined by the DOT, or other state government offices in the area served by the particular quarry. In addition, we often inventory other sizes with tighter tolerances. For example, in Maryland, we inventory 12 sizes of standard Riprap although only the 4 Maryland State Highway Administration sizes are shown below.

The following table shows rough limits of each class of Riprap. In most cases other gradation rules apply within each class.


Type Size
Alabama Class 1 10 - 100 lbs.
Alabama Class 2 10 - 200 lbs.
Alabama Class 3 25 - 500 lbs
Alabama Class 4 50 - 1000 lbs.
Alabama Class 5 200 - 2000 lbs.
Florida Bank and Shore 140 - 700 lb.
Georgia Type 3 15 - 165 lbs
Georgia Type 1 125 - 700 lbs.
Maryland Class 0 1 - 33 lbs.
Maryland Class 1 2 - 150 lbs
Maryland Class 2 20 - 700 lbs.
Maryland Class 3 40 - 2000 lbs.
North Carolina Class A 2 - 6 inches
North Carolina Class B 5 - 12 inches
North Carolina Class 1 5 - 17 inches
North Carolina Class 2 9 - 23 inches
Pennsylvania R-4 3 - 12 inches
Pennsylvania R-5 4 - 18 inches
Pennsylvania R-6 6 - 24 inches
Pennsylvania R-7 9 - 30 inches
Pennsylvania R-8 15 - 48 inches
South Carolina Class A 1 - 37 lbs.
South Carolina Class B 5 - 200 lbs.
South Carolina Class C 5 - 500 lbs.
South Carolina Class D 75 - 1000 lbs.
South Carolina Class E 500 - 2000 lbs.
South Carolina Class F 1000 - 4000 lbs.
Virginia Class A1 25 - 75 lbs.
Virginia Class 1 50 - 150 lbs.
Virginia Class 2 150 - 500 lbs.
Virginia Class 3 500 - 1500 lbs.

As with Armor Stone, Riprap specified for individual projects often include requirements regarding the characteristics of the rock used. Gradation tests, inspections of stockpiles, etc . may also be required.

Imbricated Stone -

Unlike Armor and Riprap, Imbricated Stone tends to be more rectangular with Aspect Ratios sometimes exceeding 3 to 1 with one or more flat or flattish sides. Imbricated rock is generally specified by dimension rather than weight (i.e. 1’ x 2’ x 3’ with a tolerance of at least + or - 6 inches in each dimension).

Not all quarries can produce Imbricated rock, and even those that can, may not be able to produce it in the sizes desired. Imbricated also generally requires the highest degree of picking, sorting and special handling, making it the most costly of the 3 general rock types. The wider the tolerances on the rock required, the greater the chances of producing, and the lower the cost.

Security and Landscaping Boulders -

Security Stones or Boulders:

Security Stones or Boulders are used to prevent vehicles from gaining access to buildings, areas, installations, etc. Security boulders intended to prevent unauthorized or illegal access by motor vehicles are generally 3’ to 4’ in average diameter (roughly 3500 lb – 8000 lb.). The rocks are generally placed such that no more than 4 feet of open area exists between the boulders. Smaller Security boulders (18" – 30") with wider spacing are sometimes used to create borders, direct traffic or prevent parking on the side of some roads, lots or areas. Security Boulders are much more economical than alternative security measures such as reinforced fences or walls; and are eco-friendly.

Landscape Stones:

Used to embellish the landscape, create borders, add contrast and texture. Landscape stones can be almost any shape and size. Some designers want odd shapes that serve as a monument or add mystery. Others want something that blends in and looks like it was always there. Stones can be grouped to create waterfalls, walls, borders, etc. Chesapeake Materials can provide boulders of all shapes and sizes, from a few hundred pounds to several tons.

R5 rock stockpile

Certified Armor Stone Logo

Excavator and screen

Hammer operator works through shot materials

Certified Riprap Logo

Screens placed for optimal production

VA Class 2 riprap stockpile

New Volvo Produces Riprap