Ballast Type Collection

Ballast Stone upclose

Prepared by Dr. James Craig based on research by Callahan, Miller and Craig; photographs by Karen Browning

The most common rock type present in the ballast stones recovered from the Queen Anne's Revenge shipwreck is basalt, which makes up much of the oceanic crust and which is present in many mid-oceanic islands, including most in the Caribbean. Megascopically the basalt appears as a dark gray to black fine-grained rock which is readily weathered into smooth ovoid to spherical boulders. Microscopically, the basalt is composed of plagioclase feldspar, pyroxene, and olivine and commonly exhibit a porphyritic texture with pyroxene phenocrysts.

Also abundant are samples of felsic volcanics which are lighter in color (commonly tan to greenish) and which are composed of plagioclase and quartz. These are also commonly porphyritic and display a "salt and pepper" like texture of dark ferro-magnesian minerals phenoliths in a finer grained matrix. Somewhat similar in appearance are the samples of volcaniclastics which are composed of welded fragmental materials. The fragments range in size from megascopic to microscopic.

Gabbros, which are basically coarse grained basalts, are represented by a few samples as are amphibolites, which are composed primarily of greenish amphiboles.

A few samples of quartz (probably derived from veins) and chert (cyrptocrystalline quartz probably derived from sedimentary rocks) have been observed. Limestones, recognized by the characteristic marine mollusk borings in them, are present in small numbers. Similarly, pink to grayish granites, composed of coarsely crystalline quartz, othroclase feldspar, and mica, are present as a few rare and small samples. True sandstone, composed of cemented quartz sand is rare in ballast stones but there is much ferricrete in the large concretions. This ferricrete, usually rusty red in color, is basically a recent sandstone that has been formed by the cementation of sand around the QAR site by iron released during corrosion of the many iron objects in the wreck site. These concretionary ferricretes conform to the shapes of the materials being cemented and hence are relatively easily distinguished from true ballast stones added for ship stability.

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Basalt


Volcanics


Gabbros


Quartz


Chert


Limestone


Granites


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