Navigation

Home to Minerals
Collector Forum
Event Broadcasts
Mineral Auction
Mineral Data
Posted Articles
Image Showcase
Locality References
Show Listings
Collector Directory
US Literature List
Study Material
Other Links
Rockhound Awards
Terra Search Engine
MineralCollecting.com
Advertise Here
E-Mail Webmaster

Chatbox

Maillist

Vote for this site at
TerraSearch!

New Minerals From the Old Kensington Mica Mine
You are here: MineralCollecting.org >> Posted Articles >> Article 14

by Jack Nelson
This article appeared in the April 1997 issue of The Mineral Mite, the newsletter of The Micromineralogists of the National Capital Area in Washington, D.C.
NEW MINERALS FROM
THE OLD KENSINGTON MICA MINE.

It was in April of 1991 that member Mike Eppley and I were exploring the old dumps of the Kensington Mica Mine located near the present residential community of Kemp Mill Estates in Silver Spring, Maryland. That mine, which had also been known as the Gilmore, B.H. Warner, Gilbert or Gremoses Mica Mine, no longer exists though traces of it can still be found in the community, and dump materials can still be seen on some of the hillsides overlooking nearby Northwest Branch and in the alluvium of the branch itself. (Even now, panning a couple of shovels of the streambed gravels from Northwest Branch, or the small unnamed branch that flows alongside Lamberton Drive and into Northwest Branch, will yield perhaps a hundred or so almandine crystals, some to an inch in size, and some small spessartines, schorl and staurolite crystals among the usual "black sand" minerals). Pegmatite fragments from the mine, which operated from the early 1880's until World War I, are found along the hillsides and in the streams and in the large hillside dump area adjoining the south side of the swim club at 11805 Stonington Place. It was at this dump that Mike and I were finding many schist fragments (some to hundreds of pounds) exhibiting numerous almandine, schorl (some in attractive sprays), and staurolite crystals. On this day I wandered down the hillside to the small stream paralleling Lamberton Drive, where I dug and panned a quantity of the deep stream sediments to study later at home under my new 20X basic beginner's stereo microscope I had recently obtained from Edmunds Scientific Corp. Well, for reasons I can't explain, I washed and dried the sediment, put it in a plastic bag and promptly forgot about it until early this year when I "re-discovered" it in a box under my bed. Many of our members may remember the amazing variety of microminerals obtained from the Morefield Mine near Amelia, Virginia. I know I was fascinated by the red-brown zircons, the microlites, monazites, columbite/tantalites, amazonite and spessartines from there. Well, as I began to examine the "re-discovered" material, you can imagine my amazement when I spotted some of the beautiful bluish-green amazonite fragments and then some of the wonderful red-brown zircons with dipyramidal terminations and square cross sections. I surely thought I was looking at Morefield material! The zircons were mostly single terminated prisms, many were doubly terminated and some twinned and even clusters, some of which were in a kaolin-like matrix. They ranged in size up to 2 mm. Next, I found a well formed light brownish monazite crystal just over 1 mm. Continued examination found several terminated elongated tabular black columbite/tantalite crystals as well as numerous fragments. The smallest of the sediment appeared, under 25X to 50X to be composed of many small glassy clear zircon crystals and fragments so numerous as to give the sediment a yellow glow under short-wave ultra violet light. Some very small (<0.5 mm) red, probably spessartine, garnets were found also. One of them was a cubic ferroan spessartine.! It was identified as such by Lance Kearns using his EDAX SEM during our club trip to James Madison University in February. Lance also said the yellow glow was probably caused by fluorapatite fragments as well as the clear zircons. Finding these "new" minerals at this locality has been exciting. I took advantage of the USGS's "Ask a Geologist" program by e-mail, requesting information about the pegmatite at that mine and the minerals that had been identified there. They referred me (would you believe!) to Lawrence Bernstein's book Minerals of the Wasshington, D.C. Area for that information. The minerals listed by Bernstein did not include the amazonite, zircon (both kinds), monazite or columbite/tantalite. I mounted a selection of these "new" minerals and showed them to Lance and Cindy Kearns at the micromounters conference earlier this month. Lance agreed with their identities and said the red-brown zircons could be either zircon or hafnon or one of the other two series members in between. Since I dug this stream sediment in April of 1991, Montgomery County has (in 1993, according to one of the nearby residents), apparently re-routed the course of the stream and lined the banks with large erosion-controlling rocks. I intend to return to the base of the dumps again to see if there is any trace of the area where I found this material.

Navigation

Top of Page
Home to Minerals
<< Go Back
Go Forward >>
MineralCollecting.com
TerraSearchEngine.com
SouthEastFM.org

Search the Web