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GeneralCabbage-head quartz

5th Aug 2016 17:50 UTCDan Costian

Quartz concretions with rosettes, known as cabbage-head quartz.

They are not silicified algal colonies such as stromatolites.

From the Mechanicsburg area, Cumberland Co, Pennsylvania.

http://www.mindat.org/photo-763832.html

5th Aug 2016 21:36 UTCsteven garza

Dear Dan;

No, those are more like the insides of thundereggs, the covering rock completely eroded away. Out west, they're called "onyx roses"; some are even colored a light pink. Usually, they fluoresce like a son-of-a-gun - a BRIGHT green! Since I know of NO volcanic source, anywhere near there, &, since I've collected around Mechanicsburg & several other areas closeby, &, since there used to be a rock shop near rt. 15, I'd guess you found one of their work piles, or, it was removed from THEIR property, & dumped as fill, somewhere else. The sure thing is they DIDN'T come from there, originally; probably from New Mexico - less likely from AZ or NV. Have you checked their fl yet? The brighter green they are, the further east they were. That rock shop closed over 40 yrs. ago. so, you've got some history, there.

Your friend, Steve

5th Aug 2016 21:56 UTCMilton Dye

Looks a lot like large beekite rings.

6th Aug 2016 01:49 UTCDan Costian

Hi Steven,

Thanks for your precious data about them. Yes, they fluoresce vivid green in short UV. I bought it from a dealer.

As for their origin, please check this article in Pennsylvania Geology, The Pennsylvania Geological Survey, October 1970, page 11.

http://www.dcnr.state.pa.us/cs/groups/public/documents/document/dcnr_20027571.pdf

Your friend,

Dan

6th Aug 2016 02:06 UTCAlfredo Petrov Manager

Could easily be a chert nodule with minor druzy quartz on it, from a sedimentary rock. I wouldn't be surprised to see such a thing from Pennsylvania coal country.

6th Aug 2016 02:52 UTCD. Peck

I dunno, Mechanicsburg is fairly close to Gettysburg, and Cemetery Ridge and the Round Tops are volcanic. Triassic/Jurassic like the Watchungs in NJ, the Connecticut River Valley, and Nova Scotia. I don't know where the formation goes from Gettysburg, but Mechanicsburg is only a little distance north and slightly west. Might fit your observations, Steve.

6th Aug 2016 04:11 UTCsteven garza

Dear Don;

I have to agree; the formation they're in & the time frame of the Gettysburg area volcanics would match. After reading that article Dan supplied & what you said, it makes sense.

Your friend, Steve

6th Aug 2016 15:08 UTCEd Clopton 🌟 Expert

The Mechanicsburg dealer from whom I purchased specimens of this same material at the Harrisburg show a few years ago mentioned an article in Rock & Gem, November 2006 about the material. I don't have access to back (or current) issues of Rock & Gem so I haven't read it, but I'll mention it here in case someone wants to look it up and add it to the references for the locality.

Edit: Here's a snapshot of the larger of my specimens, 5.5 cm left to right:

9th Aug 2016 11:55 UTCRalph S Bottrill 🌟 Manager

The last one especially looks like decapitated botryoidal formations, suggesting the partial infilling of concretions or vesicles?

9th Aug 2016 17:45 UTCEd Clopton 🌟 Expert

Not apparent from this photo is the fact that the aggregate has a more or less hollow core. I can imagine the aggregate freely growing outward from a nucleus in a soft medium such as clay. The edges of the "cabbage leaves" are smoothly rounded and are just irregular enough to give the impression that they stopped growing voluntarily when they reached a boundary of some sort, perhaps the edge of the chemical zone that supported crystallization, vs. having been stopped against a hard physical wall. They also appear to have grown continuously vs. being broken and "healed". I have seen similar figures on a much smaller scale on the surface of fossil corals from the Midwestern US that have been replaced by chalcedony.

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