STATE OF CALIFORNIA GOODWIN J. KNIGHT, Governor

DEPARTMENT OF NATURAL RESOURCES DeWITT NELSON, Director

DIVISION OF MINES FERRY BUILDING, SAN FRANCISCO 11

GORDON B. OAKESHOTT, Chief

VOL. 54 OCTOBER 1958 NO. 4

CALIFORNIA JOURNAL OF

MINES AND GEOLOGY

Price $1.00

SDMS DOCID# 1115136

530 CALIFORXIA J O U R N A L O F i\iI?*rES AND GEOLOGY [ V O ~ . 54

Mercury (Quicksilver)

Occurrences of the mercury minerals, cinnabar and metacinnabar, have been notecl in the Franciscan rocks of Mouiit Diablo. The only commercial cleposit of mercury in the area has been exploited a t the l f o ~ ~ i i t Diablo mine.

dloz~nt Diahlo Yiwe (Rhyne). Location: Ef See. 29, T. 1 N., R. 1 E., consistiiig of abont 100 acres on the northeast slope of the North Peak of Mo11nt Diablo about 4 miles southeast of Clayton. Ownership : Mount Diablo Quicksilver Co., Ltd., Vic Blomberg, President, P. 0. Box 133, Clayton, California.

The geology of the Xount Diablo area was described in consiclerable detail by Taff (1935). He showed that the central core of the mountain, covering abont 20 square miles, is conlposed of sedimentary (sandstone and shale), igneous (diabase, basalt, ancl gabbro) , and meta~liorphic roclis (serpentine, schists ancl ineta-chert) of the Franciscall formation of Jurassic ( ?) age. This central core is surrounded by later sedi- me~i tary rocks ranging from Cretaceous to Pliocene age totaling 35,000 feet in thickness. Taff beliered that the core of Franciscan rocks was squeezed upwarcl through the cover of post-Frailciscan rocks during the Quaternary period. This type of structure is known as a 'piercement' ancl examples ha1.e been noted a t other localities i11 the Coast Ranges. The mercury minerals occur in the sheared contact zone between the Franciscan seclinlentary rocks aiicl the intrusive serpentine especially where the serpentine has beell sltbseqnelltlp altered to silica-carbonate

, rock. d report on the geology of the 3fount Diablo mine was made by Ross

(1940). Here, the Fra i~c i sca~i strata occupies the footwall and dips abont 45" northeast~~arcl. Shear zones along the contact betureen the Franc~iscau roclis ancl the overlying serpentine control the clistribution of the ore. 1Iinor f r a c t ~ ~ r e s l~ormal to the shear zones have exercised local control over r n i ~ ~ ~ r a l cleposition.

The Mount Diablo mine is distinctive in that metacinnabar, the blacli snlfide of mercury, is one of the principal ore minerals. This mineral is co~~inioli at many mercury mines but is selcloin present in si~ficient ynantitp to be ore. Ciililabar is the other ore mineral. Minerals also founcl in the mine are marcasite, pyrite, quartz, chalcedony, car- bonates (clolomite ancl calcite), chromite, liiclrel silicate, iron s~~ l f a t e s , and epsomite.

The serpentine inass exglorecl in the mill \vorlrings was inostly - altered to silica-carbonate-rock. It averaged about 200 feet long, measured fro111 50 to l00f feet thicli, arltl extended a t least 400 feet on the dip of S. 50" E.

Regarcling the origin of the mineral deposits, Ross states: The lorles of the IIount Diahlo district appear to have been deposited from hot

wxters that derived their metallic coilstituents from distant magmatic sources. Deposition tool; place in successire stages relatively close to the surface and in g~ologically recent time. It was confincd to zones of crushing and shearing that served as channels for the rising solutions and provided adequate open spaces for deposition of the sulphides. . . . The most distinctive characteristics of the Rfount Diablo district are the reIative abundance of metacinnahar, sulphates, and gases. I n the Mount Diablo area the rock is perhaps more extensively crushed and the amount of open sp:lce that has survirecl mii~eralizativn is even greater than in other dis- tricts. These distinctive features are a11 in nccorcl with the concept that the lodes of

lot ex i n fef er re i r ~ lo.

Col. 34

~nabar, e only at the

<. 1 E., n Peak Mount )Y 133,

lerable ~iitain, ~clstone lorphic tnation r secii- 35,000 ks was ing the emeiit ' tanges. *en the leciallp ,bonate

1

1-y R,oss d dips ,en the ibution ercised

ir, the 3. This ;eat. in inerals y, car- ~lfates,

mostly ; long, feet on

rom hot sources. and in

.ng that aces for : Mount ases. I n amount

;her dis- lodes of

KO. 41 CONTRA COSTA COUKTT 531

the llfount Diablo district formed close to the surf:tce and Inore re~ei l t ly than many of the others in the Coast Ranges. This statenlent does not necessurily imply that they belong to a d~ffereiit l~eriod of ore deposition.

Deposits thus formed a re shallow as conipared with many liiuds of metalliferous lodes, but the vertic:tl range in which they may occur is fa r greater t11:rn that yet explored in the Rlount Diahlo district. Ore shoots lnax l ia \e orlgilially formed a t intervals through a vertical distance of hundreds or more, probabl;\ thousands of feet, and the deposits in this district are so recent geologically that the depth of erosion since minrralization 11robablj has not beer1 great. A more potent factor in respect to practical limits of depth is the fact that ore shoots are so small and so irregularly distributed that their positions are difficult to predict. The relativrly light load under which the lodes were formed is in par t responsible for tliese conditions.

The warm springs near the J l o u ~ l t Diahlo mine and those near other quiclisilver mines may represent d j iiig stages of the hot-spriilg acti\ ity tliat l~rtrduced the milieral deposits. l'he gases that still circulate through the lodes are lilie\vise related to hot-spring processes. I t does not follovv, lioiverer, that either r~iodern hot-spring water nearby or gases ~ i t l i i n the ruines h a \ e the same colilposition as the solutions from which the ore minerals were cleposited. The 11resence of both pyrite and ruar- casite and of both cinnab:ir and metac.inn:rl)ar shows clrarly tliat chaagrs ill the character of the solutions occurrt.d while 1nilirraliz;ition was in l)rogrc3s\. Otlier such changes have surely occurrecl since i t ceased.

It seems clear that nearly all of the su1l)liide milierals are products of the original mineralization, dr1)osited from ascending water. The metacinnal)tar is earlier than mu& or all of the cinnabar. The cinnabar, wliich is tlie more stable form of yuick- silver sulphide, m:iy have formed in part by in^ ersioii from the ]>reviously crystal- lized metacinnubar. A t all erents, i t seems clear that the m~tacinnnbar ill the crystalline aggregates of botrj-oidal form is not a s1il)ergelie product, a s this minrral is commonly supposed to be. Chemical data, recently summarized by L)reyer [1940] show that metacirinabar may be formed from rising solutions in ail acid eliviron- melit and may invert illto cil~nahar.

The presence of cinnabar on the northeastern slope of Mount Diablo was known since boyhood to the oldest Indians in the area and xas used by them in preparatioii for tribal ceremonies and nar-like acl- ventures. An early account (Mining and Scientific Press, 1865) states that the deposit was located about 1863 by a Mr. Welch who sank a 33- foot shaft to intersect the ore at depth, and that both native mercury and cillilabar could be obtained by paniiii~g the soil removed in this work. Locatioils were subsequently iizacle both north and south of the original claim and a placer locatioll was made at a lower elevation where both mercurx and ciilnabar were recovered by panning.

A short period of ,production occurred from 1875 to 187'7 but the exact quantity produced is unknown. A11 old report (Ireland 1888) states "it is said to have produced 85 flasks of quicksilver per month7'. Judging by the size of the dunips, however, subsequent operators have expressed doubt t h a t production was lllaiiitaiiled at this rate Tor any appreciable time. Consequently we have tentatively credited this period with a total production of 1000 flasks.

Except for sporadic efforts the mine lay idle until 1930 when it r a s reopened by the Mount Diablo Quicksilver Mining Compaiiy who made a small production in 1930. I11 December 1930 the 31t. Diablo Quick- silver Co., Ltd., was organized under the laws of the state of Kevada to acquire the property and to develop the mine under lease royalty arrangements with operating companies. Some exploration work was done In 1931 and a small productioii was iliade in 1932 by treating the ore in a 7-tube retort. C. W. Ericksen operated the mine during the first part of 1936 and installed a rotary furnace t o treat the ore. The first major lessee was the Bradley Mining Company, San Francisco, who began operatiiig the mine in the latter part of 1936.

332 CALIFORNIA JOURKAL OF XINES AND GEOLOGY p o l . 54

50 0 5 0 100 F E E T t I I I I I I I

SCALE

C 0 .- + 0

E L

0 - C 0 U m . - U C 0 L

LL

60-FOOT LEVEL

126 - F O O T LEVEL

2 0 5 - F O O T LEVEL \ F I G ~ R E 3. Section thruligh Xi11 TI-orlrings. Sit. Dinhlo mercury mine (from U. S.

C;evlogicnl Sur rey Bull. 922-S, p. 45).

The de~elopnient of the deposit has been localized in two areas: the Rhyne-Jones and the Jlill TT-orkiligs. The Rhpne-Jones area (about 1500 feet west of the nlillsite) was the locns of the earliest wldergrouncl mining. This work i~~cluclcclAhe Rhylie ancl the Jones tunnels, consisting of about 1200 feet of aclits aiid drifts, which explored a breccia zone trending northwestward. Sollie mining m-as clone by the Bradley ilIining Company in the Ehy~ie-Jones area. Nost of their milling ho15~ever was co~iceiitrated on the shear zone a t the Mill worliings which hacl beell ignored or overlookecl in earlier work.

ILill ~vorkings 11-ere opened or extended in 1936 ancl tlie surface excavations eveli t~~ally incluclecl 4 benches and a glory hole. An adit with portal belov- tile ~iiill proviclecl entry to the uiidergrouncl workings. Three lower lei-els a t 126. 160, aiid 205-foot points were reached by winzes. The workings of the mine, inclucling the surface cuts, extended tlirough a vertical distance of about ,500 feet aiicl aggregated about 4000 linear feet. Stopes areragecl about 20 feet in wiclth ancl extended from 100 to 150 feet in length.

No.

'1 in& i11 mir in : Frz 8 n ces! w at 194 Sor con

'1 wa1 mir con sha wit 2 I "bl D -r 1

recc Dej con the zon

C

cab tor: the a. 5 ~vhi

I JOE ope sul dill

I the fee f 01; fou ope tio. mil

1 a d ha( 6101

iiit

-01. 54

F E E T

;: the 1500

-ound istiiig zone

:ining r TT-as been

trface L adit. sings. ?d by 2nded ,4000 from

SO. 41 CONTRA COSTA COLTSTT 533

The Bradley 114iiiiiig Company produced niercnry from 1936 to 1946 inclusire. As the terliiiiiation of TTTorld W a r I1 approached. a clecline in the price of inercary began m-hich e ~ e i i t ~ ~ a l l y halted the profitable mining of the metal. Shortly after the mining of niercurr ore encled in 1946, crushers IT-ere installed to proclnce crushed rock from silicified Franciscan sandstone. The plant was in colitiiiuous operation for about 8 moilths but competitioii from more fa~rorablp located plants forced cessation of this operation. Prodnctioi~ of crushed rock in March 1951 was on an intermittent basis. Xo inercur7 procluction was made from 1947 to 1951 and the coin pan^ surrendered the lease in the latter year. Some operating data covering the productive period of the mine was coiiipiled by the compaiiy and is presented in table 4.

The price of mercury zoomecl npmrard in the latter par t of 1950 when war broke out on the Korean peaiiisula. About the nliddle of 1951 the mine was leased to Roniiie E. Smith, Dallas, Texas. Ope]-ations were colicelitrated in the open pit at the Mill ~vorkiiigs. Two horseshoe- shaped benches with 30-foot faces \yere mined using a diesel shovel ~ i t h a 1-yard dipper and a Caterpillar loader. The ore ~ v a s loaclecl to 2 Enclid dump trucks for the short haul to the mill. The ore was "burlied" in the rotary furnace and condenser soot ~ v a s treated in a D-retort: Twelve men were employed.

As a result of the work during 1951-1952 and its past production record, the U. S. Governmelit on June 5, 1953 granted the mine a Defense Minerals Exploration loan in the aniolnnt of $125,000. This colitraet called for underground exploration beneath the mill pit tvith the hope of finding a niiiieable ore body a t greater depth in the shear zone.

A 40-foot headframe, carrying a %foot sheaye strung n ~ i t h a $-inch cable, was erected and a 40-horsepower hoist v a s installed. A11 esplora- tory, 2-compartment shaft (4+ by 84 feet in the clear) was sunk 011

the north side of the pit. A t a poillt 300 feet be lo^^ the sliaft collar, a 5 by 7-foot drift was heacleci southwestward tot~arcl the shear zone 13-hich lay a t an estimated clistallce of 120 feet.

I n Jaiiuary 1954 Smith assigliecl his lease to J. L. Jonas and J. E. Johnson. Shortly thereafter the nes3T lessee eaconnterecl ~mdergroniid operatin8 difficulties owing to the presence of gas (hydrogen sulfide, s~ l l fu r dioxide and niet'hane) . The ivine was closecl and relnained idle during the reiliaiiider of the year.

I n February 1955 the Cordero &lining Conipaiiy, Palo Alto, obtainecl the lease and colnpfeted the esploratioii contract which called far 910 feet of crosscuts and drifts 011 the 300-foot level. It was reported that four leads were niicovered and a siiiall tonnage of 3- to 7-pound ore was found. The showiiigs were not considered sufficient to warrant further operation by the cornpan? and the lease v a s teriniliatecl. No certifica- tion of discovery mas iiiade b~ the Defense Minerals Exploration Ad- ministration.

I n 1956 the Nevada Scheelite Company leased the iliine ancl illstalled a deep-well pump (550 gallons per minute) to remove the water whicl~ had risen to a point 112 feet below the collar of the shaft. Since the down-stream ranchers objected to the discharge of acid liiiiie water into the creek this worlc was suspended. Attentioli TYas then directed

CALIFORNIA J O U R N A L O F NINES AND GEOLOGY [Vol. 54

to A SUI

r el

CU

eo in( fat W:

bli ro

XO. 31 COS-TRA COSTA C O U S T T 535

to the open pit 15-here sollie esploratioil was done using ~vagoii drills. A sinall tonnage of retort-grade ore mas developed. Since this was not sufficient to satisfy the requirements of the company the lease was reliiicyuished.

No production of mercury was reported cluring or since completion of the DMEA contract. The mine has remained idle from 1956 to date ( Ju ly 1958) and the shaft and underground t~orkings have filled with water. The flow of water on the 300-foot level is reported to be 150 gallons per minute. During the stormy winter seasoil the undergrouiici water can be diverted into the creek without damage to doll-i-nstream neighbors. During the surnnier and period of low-creeli flow however, the iiliae water must be pumped to surface sumps and aerated or treated with liine before diversion.

The mine ore traiisfer system coilsists of a 50-ton coarse mine-ore bin, feeding the ore to a 10 by 12-inch Pacific jaw crusher, dropping the miiins 14-inch crushed ore to a 125-foot conveyor belt which con- veys and deposits it in a 90-ton fine ore bin.

The ore treatment plant coiisists of a 42-foot Qould rotary counter- current furnace of 50-ton per clay capacity. I t ' s equipped with a dust collector, condensers, exhaust fail and stack. Auxiliary equipment inclucles: D-retort, mud machine, 30 cubic foot plant compressor. 210- foot air compressor (cliesel driven), 15,500-gallon fuel storage tank, water well system. Buildings include a bottling ancl flask storage house, blacksmith shop, equipment shop, warehouse, 7-room bunkhouse, 6- room cookhouse, and 3 residence houses.

Total reported production throughout the entire life of the mine has been slightly over 11,000 flasks.

Mineral Springs

The medicinal value of mineral waters has been recognized for centuries. During the 19th century California demonstrated that her niineral springs v-ere as valuable ancl efficacious as any in the world. Health resorts that were established at the site of the niost accessible and salubrious spriiigs enjo:~ed great vogue until the autoinobile became a coiiirnon means of transportation about 1930. Thereafter the population grew niore restive aiid the popularity of the spas cleclined.

Most of the springs of Contra Costa Count)- were described by \JTaring in 1915. The Twenty-seventh Report of the State IZineralogist contains a summary of TTTariiig's description aiid some data on the waters of AlhiGiibra, Byron, Ferndale, Pilie Canyon and- Sulfur Springs.

Mineral water has been produced almost coiitiiinously in Contra Costa County from 1896 to 1951. Data on the quantity and value of millera1 water bottled for sale are ilicluded in the county statistics from 1896 to 1946 inclusive. Xiiice 1931 Alharnbra Springs south of Martinez has been maintained in staiicl-by conditioii but has made no production. Oak Springs water has not been usable since 1951 owing to the encroachment of local inhabitants.

A table sumniariziiig data 011 the springs which have produced water for sale in the county will be found at the end of this report.