Southwestern Arkansas Mercury Mining District
by Art Smith
Member of the Houston Gem & Mineral Society
artsmithite@msn.com

T

he Southwestern Arkansas mercury mining district is a one mile wide east-west band on the Athens Plateau, the southernmost portion of the Ouachita Mountains. This narrow band extends from western Clark County through Pike County into eastern Howard County. Further west in Sevier County, but not contiguous with the mercury district is the Arkansas antimony mining district which has a separate mineralogy and mining history. However, stibnite is common in the western end of the mercury district and absent on the eastern end. All of the mercury mineralization is in the folded and faulted east-west trending anticlines and synclines of the Paleozoic age Stanley Shale which is composed of about 25% sandstone and the Jackfork Sandstone. Although the shales may contain some mineralization, all the ore occurs in sandstone as disseminations and fracture and vein fillings. Some of the sandstone is so indurated that it appears more like a quartzite, and indeed, it is often called a quartzite.

Map of area

The first documented discovery of cinnabar in the district was in 1930. Following an announcement of the discovery by the state geologist in 1931, the size of the district and mining in it developed rapidly. Between 1931 and 1937 the district produced 4736 flasks of mercury from numerous mines and prospects. Then production and mining lagged for two years but increased dramatically with the marked price increase of mercury during 1940. The price of mercury was high, and so mining flourished through 1943 but then dramatically decreased with lower prices and depletion of known reserves. By 1947 the district was dead, and the only subsequent recorded production was 11 flasks in 1965 (Clardy & Bush 1976). Total production for the district was about 12,500 flasks with most of it coming from less than 10 mines, but over 50 mining companies had operated in the district during its 15-year period of activity. Discoveries were made strictly from surface outcrops which were followed into the subsurface. Very little core drilling was done to prove new reserves or to find new deposits, and most if not all was done by the U.S. Bureau of Mines during the war years and does not seem to have been very successful

The most notable deposits are those on Bemis Hill, Parker Hill, Parnell Hill, and the Bell, Caddo, U.S., Humphrey, and Gap Ridge mines. Perhaps the most interesting name was Parnell Hill’s Bloody Cut, no doubt named for the abundant cinnabar showing on the walls of the cut during mining. Although all of the cinnabar has been removed, the Bloody Cut and other pits and cuts can be observed along the wooded shores of Lake Greeson in the Cowhide Cove Recreation area. The mining activity occurred before dam building and lake formation, as was the establishment of the recreational area. With some diligent searching of the associated dump piles along the lake shore and in the woods, good traces of cinnabar still can be recovered.

Table 1 is a list of minerals reported from the district. Most of these occur only as microminerals. Larger specimens are uncommon but are available occasionally from older collections, particularly bright red sandstone with richly disseminated cinnabar. The cinnabar in sandstone helps distinguish it from Terlingua, Texas cinnabar specimens which are in a limestone and are much more numerous. Solid crystalline cinnabar may occur as vein and fracture fillings, and small crystals may occur in cavities. Some Arkansas locations have a red ocherous goethite-hematite mixture that masks much of the cinnabar or that can give an impression that there is more cinnabar present than there really is. Bright colorless transparent quartz crystals are not uncommon. They may be completely or partially doubly terminated and are more like Herkimer quartz crystals than most Arkansas quartz from the central Ouachita Mountains. They may reach 4 cm across, but most are smaller, and they are particularly attractive and desirable with red cinnabar crystals or inclusions or with cinnabar or stibnite. Most of the cinnabar crystals are bright to dark red and under 4 mm. They are not as well formed as the Chinese cinnabars and can be seen as equant, slightly rounded, single and twinned crystals, rods, some with branches, or fibers. Most of the other crystallized minerals occur only as micro crystals, but larger specimens containing them are rarely available. Calomel fluoresces a deep red under short-wave radiation and is present as smears and coatings. However, it is usually difficult to discern without a microscope even on larger specimens except with an ultraviolet light.

BIBLIOGRAPHY
Clardy, B. F. and W. V. Bush 1976 Mercury District of Southwest Arkansas. Arkansas Geological Commission Information Circular 23.

McIlwaine, R. B. 1944 Southwestern Arkansas Mercury District, Howard, Pike, and  Clark Counties, Arkansas. U.S. Bureau of Mines War Minerals Report, unpublished, 41p.

Reed, J. C. and F. G. Wells 1938 Geology and Ore deposits of the Southwestern Arkansas Quicksilver District. U.S. Geological Survey Bulletin 886-C.

Roberts, A. C., M. A. Cooper, F. C. Hawthorne, R.A. Gault, J. D. Grice, and A. J.
Nikischer 2003 Artsmithsite, a new Hg1+-Al phosphate-Hydroxide from the Funderburk prospect, Pike County, Arkansas. Canadian Mineralogist 41:721-725.

Sohlberg, R.G. 1933 Cinnabar and associated minerals from Pike County, Arkansas

American Mineralogist 18:1-8.

Stearn, N. H. 1936 The cinnabar deposits in southwestern Arkansas. Economic Geology 31:1-28.

Table 1:

Minerals of the Southwestern Arkansas Mercury Mining District

Mineral

Chemistry

Description

Reference

anglesite (?)

PbSO4

white coating on galena

Clardy & Bush 1976

artsmithite

Hg1+4Al(PO4)2-x(OH)1+3x

white, fibrous, xls micro, late.

Roberts et al. 2003

barite

BaSO4

white to colorless, coarsely xline

Reed & Wells 1938

cacoxenite

AlFe3+24(PO4)17O6(OH)12.~75H2O

spheres, yellow fibers

EDS analysis

calcite

CaCO3

white to clear, uncommon

Clardy & Bush 1976

calomel

Hg2Cl2

white to yellowish coatings

Sohlberg 1933

cinnabar

HgS

bright to dark red crystals

Sohlberg 1933

dickite

Al2Si2O5(OH)4

white powdery coatings

Clardy & Bush 1976

edgarbaileyite

Hg1+6Si2O7

orange, crystalline

EDS analysis

eglestonite

Hg1+4Cl2O

yellow crusts turn black

Clardy & Bush 1976

fluorapatite

Ca5(PO4)3F

white, 2-3mm discoidal xls

EDS analysis

fluorite

CaF2

 

reported McIlwaine 1944

goethite

a-Fe3+O(OH)

red, yellow, brown, earthy & botr.

Reed & Wells 1938

hematite

a-Fe2O3

mixed with goethite

Reed & Wells 1938

livingstonite

HgSb4S8

dark gray globular masses

Clardy & Bush 1976

mercury

Hg

liquid silver spheres

Clardy & Bush 1976

metacinnabar

HgS

dark red to black coatings, xls

Clardy & Bush 1976

opal

SiO2.nH2O

hyalite, clear to white coatings

Clardy & Bush 1976

perhamite

Ca3Al7(SiO4)3 (PO4)4 (OH)3.16.5H2O

tiny white spheres

EDS analysis

pyrite

FeS2

smears, small masses, cubes

Clardy & Bush 1976

quartz

SiO2

Clear, colorless to sli. smoky xls

Reed & Wells 1938

siderite

Fe2+CO3

brown translucent xls in deeper mines

Reed & Wells 1938

stibnite

Sb2S3

gray acicular crystals, inclusions

Stearn 1936

stibiconite

Sb3+SbO5+2(OH)

pale yellowish stibnite pseudomorphs

Sohlberg 1933

terlinguaite(?)

Hg2ClO

yellow, crystalline,turns green-gray

EDS analysis