Definitive banding and translucency are disinctive characteristics of the only true Maryland agate find of which we are aware. The locality appears to be around a contact point between siliceous (quartz) rock and serpentinite rock within a small plot between I-70 and Catonsville where a Baltimore County geological map shows serpentinite to be dominant.
A clearer macrocrystalline quartz druse accounts for the translucency evident on polished slabs as well as blue to
A potential for questioning the legitimacy of agate nomenclature asserts itself in various official definitions that specifically categorize agate as cryptocrystalline with conchoidal fracture. While a limited amount of chalcedony is present in a few of the Baltimore County specimens as shown at right, most are primarily quartzite with a healthy presence of macrocrystalline quartz.
For clarification, we contacted John S.White, Past Curator-in- Charge of of the National Gem and Mineral Collection at the Smithsonian as well as one of the world's most frequently published authors on questions relating to the integrity of species nomenclature. His response:
I have seen lots of agate boulders split without them exhibiting conchoidal fracture. However, a chip from them might well do so. In any case, if this is quartz and it exhibits colorful banding, then I see no problem with calling it agate. Lots of agate has bands that are colorless quartz xls, especially on the inside of nodules as the very last thing to grow. Quite often “agate” is in the eye of the beholder and lots of stuff that you nor I might not care to call agate is called agate by those who have it. This material does appear to be banded and very colorful and I would not mind having a cab of it myself.
Clearly, the banding and the translucency define the material as agate. They also raise questions relating to Maryland's Official State Gemstone, known as "Patuxent River Stone" and described on the State of Maryland's Kid's Page as follows:
The Patuxent River Stone is actually an agate, a cryptocrystalline form of quartz. Found only in Maryland, the Patuxent River Stone's colors of red and yellow reflect the Maryland State Flag.Patuxent River Stone, of course, is neither banded nor cryptocrystalline. Even worse, until after the publication of our previously referenced post about Patuxent River Stone on October 29, 2010, it was still being called"agatized dinosaur bone” as well. In truth, Patuxent River Stone is nothing more than quartzite with some red and yellow hues.