There are three alkaline
intrusions in Arkansas, that I will deal with on these pages. I first
tried to put them on one page, but you would have gotten a lame arm
from scrolling through three pretty long mineral lists.
I would like to thank László
Horvath and J.Michael Howard for information and the latter for
specimens, too. Thanks also to Peter G.Seroka for information and the
To go to the localities:
Sulphur Springs (aka Wilson Springs mines)
- Perry and Conway Counties:
Sills, dykes, plugs. Shonkinite, syenite, aegirine-granite.
Aegirine, amphibole grp., analcime, biotite, melanite, nepheline,
- Montgomery County.
Carbonatite, very small.
- V Intrusive:
Complex dyke system. Malignite, melteigite, ijolite, syenites,
pulaskite. Fluorite, pyrite.
- Little Rock: Extension of
Granite Mt., probably 50x30km, which would be North America´s
largest intrusion. Nepheline syenties. Aegirine, amphibole grp.,
analcime, biotite, feldspar grp., nepheline, pyroxene grp.,
- Saline Co.: Probably
outcrop of Little Rock intrusion. Nepheline syenites, tinguaite,
monchiquite, overlying bauxite deposits (mining). Aegirine,
aegirine-augite, analcime, arfvedsonite, astropyhllite, biotite,
diopside, nepheline, perthite, plagioclase, sodalite.
- Prairie Creek (plus
Kimberlite Mine, American Mine, Black Lick): 700m in
diameter. Lamproite, breccia tuff, mica peridotite. Amphibole grp.,
clinopyroxene, diopside, olivine, perovskite, phlogopite, priderite,
richterite. Exploited commercially for diamonds !
- Woolley, A.R.: Alkaline Rocks
and Carbonatites of the World. Part 1: North and South America.
British Museum (Natural History), London, 1987