Fax: 704-721-4657 Website: www.reedmine.com Email: reedmine1799@msn.com

9621 Reed Mine Road Midland, NC 28107 Phone: 704-721-4653

Drilling and Blasting

Reed Gold Mine State Historic Site

Blasting had been developed by the Chinese prior to

1,000 A.D. Yet, the first instance of blasting in rock

excavation occurred in 1627. Kasper Wiendl placed

blasting powder in cracks within a rock and detonated

it using slow match, a loosely spun cord with salt pe-

ter.

By 1683, a rock drill was developed in Saxony. The

drill consisted of a steel rod with a star-shaped bit at

one end. This drill was held against the rock face and

turned after each blow with a sledgehammer. This

form of drilling is termed “double jacking” because

two Cornish miners, or “jacks,” would drill the holes.

The drilled holes were 1-1/2 inches wide and 18 inches

deep. Clay, sand or rolled tin lined the holes to pre-

vent the black powder from becoming damp and use-

less. A prescribed amount of powder was inserted

using a hollow tube. The loaded hole needed to be

capped with wood (plug shooting) or more commonly

clay (stemming). A trail of black powder over boards

led to the charge. A stem connected the flame to the

powder. Once the charges were ready, everyone ex-

ited the mine except the blaster, who would light the

various fuses, confirm that each fuse was burning cor-

rectly, and then leave. A safety fuse, developed by Wil-

liam Bickford of Cornwall in 1831, replaced this

method. This fuse was similar to rope and had a black

powder-filled core.

A pneumatic, or air-powered drill, replaced slow and

laborious double jacking. Ascanio Sobrero invented

nitroglycerin in 1846 to be used instead of powder,

but it proved to be extremely dangerous. Nitroglyc-

erin soaked into Fuller’s earth or sawdust and pack-

aged in waxed paper rolls called dynamite (developed

in 1867), however, was a lasting improvement.

Gold: The Mechanics of Mining

Reed Gold Mine State Historic Site

www.reedmine.com

The coolest place in North Carolina is a hole in the ground!

Developed in Mexico, and also called a “drag mill,” the

arrastra, is similar to a Chilean mill. The stones turn in

a circle around a center post. However, on the ar-

rastra these stones were dragged over a flat surface,

with the ore between the base and the drag stones,

rather than inside a trough. Often the arrastra was

used on ore that had already been through the early

stamp mills, to crush it more finely.

Because they were simpler, easier to build, and

cheaper, arrastras became more popular than the chil-

ean mill by the 1930s. Both arrastras and chilean mills

were slow compared to stamp mills.

Chilean Mills

The chilean mill usually featured two stone wheels

perhaps five or six feet in diameter (called runners)

that rotated around a shaft set into a circular stone

base. The base contained ore, water, and mercury.

Heavy wheels broke the ore into fine particles. The

base or “bedstone” had a circular trough cut into the

top. The vertical runner stones were held in place by a

wooden frame. This frame was attached to a center

post that was turned by a series of gears using either a

steam engine or horse (or mule) power. The stones

would circle the base seven to ten times per minute.

The stones, fashioned by stone masons, were difficult

to repair or adjust. This made them rather expensive

and eventually led to the widespread use of the ar-

rastra in place of the chilean mill.

The chilean mills located on Upper Hill at Reed Gold

Mine were able to grind two tons of ore in 24 hours.

The ore was broken up with sledge hammers, sent

through a stamp mill, then shoveled into the mill

trough. The trough was lined with mercury and had a

constant flow of water to insure maximum amalgama-

tion. It is not known how chilean mills came to North

Carolina, but by the 1830s this type of mill was the

primary means of recovering gold used throughout the

state. They remained popular through the mid-1800s.

Arrastras Stamp Mills

The stamp mill is a modification of the ancient technique

of breaking ore by the use of a mortar and pestle. Early

European mills were constructed of wood, with stone

stamps, and were bound together with rawhide and

wooden pins. The only major change in the stamp mill

during the next three centuries was the substitution of

iron for stone in the stamp heads and mortar.

Miners would deliver ore to the mill house where is was

crushed into pieces one to two inches in diameter. The

ore was then released into the hopper at the stamp mill

itself. By 1895, newer stamp mills could have been

equipped with automatic feeders that passed ore into the

mortar at a measured rate.

The ore would be mixed with water, under the crushing

action of the stamps. Starting around 1890, miners placed

mercury in the mortar box, as well as on the copper or

silver amalgamation plates, to catch the released gold. A

brass or tin screen was placed across the front of the

mortar box to prevent excessively large particles of ore

from escaping.

Amalgamation plates were placed in the mortar box and

on a table sloping away from the discharge of the mill.

The plates were coated with mercury and held gold sepa-

rate from the water-rock mixture that flowed over them.

The plates were scraped regularly and the amalgam was

saved. With proper cleaning and a suitable grade of ore, a

miner might recover a fair percentage of the free (non-

sulfured) gold in the water-rock mixture. A five-stamp

battery might crush five tons of ore in 12 hours. Though

faster than chilean mills or arrastras, stamp mills were

not necessarily more efficient. If the correct degree of

fineness could not be maintained, finer gold might simply

float away with the tailings, while ore that was too coarse

would not obtain enough contact with the mercury for

amalgamation (process of bonding gold with mercury). In

the 1930s stamp mills were replaced by ball mills.

Top: Arrastra Bottom: Apron table and mortar box of Stamp Mill. Chilean Mill