Download the entire report in Ballast
Dr. Stephen Pollock and Dennis Bratten of the University of Southern Maine, Geology Department slabbed and visually examined 46 stones randomly picked from the shipwreck’s ballast mound. A small number of stones was initially chosen as a good starting point to determine preliminary rock classes and types.
Table V. lists the rock classes and types identified thus far. The most common ballast encountered in the sample consists of a quartzite-like mineral known as arenite (39.12%) followed by the sedimentary rock, micrite (19.55%); and the igneous rock, basalt (13.03%). Other types in the sample include: quartz (8.68%), tuff (4.34%), and single examples of aphanite, granite, calcarenite, jasper, and one unidentified specimen. Based on this suite of types, the sample is not inconsistent with rocks and minerals associated with the Caribbean basin or a Mediterranean region. Further analysis may allow the determination of a more precise location.
In the very near future, the samples will be thin-sectioned and examined by X-ray crystallography and microscopically under polarized light. These techniques permit the determination of minerallic composition and texture (size and orientation of crystal grains). Using this data, geologists can more precisely describe and correlate the ballast geographically.
| Type | Class | Subclass | Example | Comments | Quantity |
|---|---|---|---|---|---|
| *Data and analysis by Stephen Pollock and Dennis Bratten, Department of Geology, University of Southern Maine, July, 1995. | |||||
| Igneous | extrusive | mafic (iron rich) | amygdaloidal basalt | 1 | |
| fine-grained basalt/diabase | 1 | ||||
| porphyritic basalt/diabase | 4 | ||||
| felsic (siliconrich) | aphanite porphyry (rhyolite?) | quartz and alkali feldspar phenocrysts or feldspar rich | 2 | ||
| crystal tuff | weakly aligned feldspar | 1 | |||
| welded tuff | shards? | 1 | |||
| intrusive | granite | equigranular hollocrystalline | 1 | ||
| Sedimentary | carbonate | buff-colored micrite | 1 | ||
| “vuggy” micrite | 2 | ||||
| gray burrowed laminated micrite | 6 | ||||
| calcarenite | fine-grained | 1 | |||
| clastic | tan to buff colored quartz arenite | possibly quartzite or rhyolitic volcanic | 6 | ||
| gray quartz-richarenite | possibly quartzite, thin quartz veins | 12 | |||
| Other | milky-veined quartz | 4 | |||
| jasper | breccia? | 1 | |||
| unidentified | 1 | ||||