QUARTZ.

The crypto-crystalline (obscurely crystalline) varieties of Quartz are

many. The following may be named as the most important: Chalcedony,

carnelian, sard, chrysoprase, prase, plasma, bloodstone, agate, onyx,

sardonyx, jasper, basanite, flint and hornstone. The distinctions

between the different varieties are loose and are differently stated by

different authorities. Some class agate, onyx, sardonyx, plasma and

carnelian together as varieties of chalcedony, while others consider

chalcedony a simple variety. The chalcedonic varieties of quartz agree

in having a fibrous structure and in being somewhat softer (hardness 6½)

and somewhat lighter (specific gravity 2.6) than crystallized quartz.

They also break with more difficulty than quartz, being very tough. The

varieties differ among themselves, chiefly in color.

Common chalcedony has a waxy luster and is usually translucent rather

than transparent. The transparent forms are known as “oriental,” the

translucent as “occidental” chalcedony. Common chalcedony has little

color, shades of gray and blue being the most common, although other

tints occur. It usually presents rounded surfaces which have grape-like,

kidney-like or stalactitic forms. It occurs coating other rocks or

minerals or lines cavities or fills veins and clefts. It is never, so

far as we know, deposited in any other way than by percolating waters.

At Tampa Bay, Florida, the waters containing chalcedony have penetrated

corals and preserved them, often giving forms showing the shape of the

coral outside and a cavity within. Throughout the “Bad Lands” of the

West, clefts in the hills are often filled with sheets of chalcedony

varying in thickness from that of thin paper to nearly an inch. These

chalcedony veins ramify in all directions and often extend for many rods

without interruption.

When the chalcedony is penetrated by branching forms of manganese or

iron oxide the forms known as “mocha stones” and “moss agates” are

produced. These are not due to vegetation any more than the similar

forms of frost on our window panes. They are purely mineral in their

origin. Moss agates are found in numerous localities in the States of

Utah, Wyoming, Colorado and Montana. In the opinion of Mr. George F.

Kunz “no stone that is used in jewelry in the United States is cheaper,

more beautiful or more plentiful than the moss agate.” The best occur as

rolled pebbles in the beds of streams. The name, “Mocha stone,”

sometimes applied to moss agates is either due to the fact that those

first used came from Mocha in Arabia, or it is a corruption of the word

moss agate. The finest moss agates now known come from India. A white

variety of chalcedony containing minute blood red spots is known as St.

Stephen’s stone. Chalcedony was formerly used much more and more highly

prized than at the present time. It was especially employed for seals

and rings, but also for plates, cups and vases. These were often

engraved in the most elaborate manner, the hardness and toughness of the

stone making it well adapted for this purpose. The sentiment of the

stone is: “A disperser of melancholy.” The name chalcedony is from

Chalcedon, a city in Asia Minor, where the original chalcedony was

found. This mineral was probably not like our modern chalcedony,

however, being more probably a green quartz. This chalcedony is

mentioned as one of the foundation stones of the Holy City in the Book

of Revelations.

[Illustration: QUARTZ (obscurely crystalline.)

LOANED BY FOOTE MINERAL CO.]

Left column:

Bloodstone, polished (India.)

Tiger Eye, polished (South Africa.)

Center:

Chrysoprase, polished (Arizona.)

Agate and Carnelian, polished (Lake Superior.)

Right column:

Jasper (Germany.)

Ribbon Jasper, polished (Siberia.)

Carnelian is a red variety of chalcedony, sard a brown variety. All

gradations between these shades of course occur, those of the reddish

cast being the most common. The most highly prized color for carnelian

is a deep blood red, appearing darker red in reflected light. The

lighter red and yellowish shades are less desirable, stones of these

shades being known as “female carnelians,” while those of the darker

shades are known as “male” carnelians. The colors are due to oxides of

iron and can sometimes be changed by heating. Thus the yellowish and

brownish carnelians being colored by iron hydroxide can be changed by

heating to red, the water being driven off and iron oxide left. The

heating may be done in the sun or by some other slow means. Even olive

green stones are changed in India to red by this process. The color may

also be introduced artificially by allowing the stones to lie in a

mixture of metallic iron and nitric acid, or of iron sulphate for a

while. In this way the iron salt needed for the coloring matter can be

absorbed by the stone and this is changed afterwards to oxide by

heating. The best carnelians come from India, but good stones are also

obtained in Siberia, Brazil and Queensland. Carnelians are cut usually

in oval and shield-like shapes and were much employed by the ancients

for intaglios. They believed them to have the power of preventing

misfortune and they were much worn as charms.

Sard of typical brown color is much rarer than carnelian and possesses a

high value. In other respects it is like carnelian. The sardius

mentioned in the Bible as forming one of the stones of the High Priest’s

breastplate was undoubtedly a carnelian. The name was derived from

Sardius, a city of Lydia whence fine carnelians are obtained. The name

carnelian is according to some authorities derived from the Latin word

caro, carnis, flesh, and refers to the color of the stone, or according

to others it is from the Italian word carniola which has the same

meaning.

Chrysoprase and Prase are terms applied to an apple green to bright

green chalcedony or compact, jasper-like form of quartz. Some

authorities, however, call the green chalcedony plasma and restrict the

term chrysoprase to the green compact quartz. The terms cannot be

accurately distinguished. Most chrysoprase now in use comes from

localities in the province of Silesia in Germany, where it occurs in

thin layers and veins in serpentine. The green color here is due to

nickel oxide which is present in the stone to the amount sometimes of

one per cent. The first discovery of the stone is said to have been made

by a Prussian officer in 1740. The stone was especially fancied by

Frederick the Great so that he had two tables made of it and used it

frequently in mosaics. The color fades with light and heat, but it is

said can be restored by burying the stone in moist earth for a time.

Beautiful chrysoprase comes from India and there are a few localities in

our own country where it is found, it being usually associated with

nickeliferous deposits. The name chrysoprase comes from two Greek words

meaning golden leek and refers to the color of the stone.

Plasma, as already stated, is a name applied to green chalcedony, or by

some to green jasper. The name comes from the Greek for image and shows

that the stone was largely used for seals and other engraved work. Most

of that known at the present time comes from India and China.

Bloodstone is a variety of plasma containing spots of red jasper looking

like drops of blood. Another name for bloodstone by which it was chiefly

known by the ancients is heliotrope. This name is derived from two Greek

words meaning “sun turning” and refers to the belief that the stone when

immersed in water changes the image of the sun to blood red. The stone

was often used by the ancients for carvings representing the head of

Christ, and one fine specimen of such work may be seen in the Field

Columbian Museum. The ancients had a tradition that the stone originated

at the crucifixion of Christ from drops of blood drawn by the spear

thrust in his side falling on a dark green jasper. The stone takes a

beautiful polish. To be of the best quality it should have a rich dark

green color and the red spots should be small and uniformly distributed.

The supply is obtained almost wholly from India, especially from the

Kathiawar Peninsula west of Cambay, whence agate, carnelian and

chalcedony are also obtained. Fine examples have also come from

Australia and a few from Brazil. In present usage bloodstone is the

“birth stone” of the month of March.

“Who on this world of ours their eyes

In March first open shall be wise,

In days of peril firm and brave

And wear a bloodstone to their grave.”

Agate was described in the June number of this magazine.

Onyx and sardonyx are varieties of agate in which the layers are in even

planes of uniform thickness. This structure enables the stone to be used

for engraving cameos. As is well known, these are so made that the base

is of one color and the figure of another. This art of making cameos

reached a high degree of perfection among the Romans and many superb

examples of it have come down to us. The word onyx means a nail (finger

nail) and refers to some fancied resemblance, perhaps in luster, to the

human nail. Sardonyx is a particular variety of onyx in which one of the

layers has the brown color of sard. Other kinds of onyx are those known

as chalcedonyx and carnelionyx in reference to the color of the

intervening layers. So-called Mexican onyx is composed of quite a

different mineral from the onyx here considered, it being made up of

calcite rather than quartz. Mexican onyx can be scratched easily with a

knife while quartz onyx cannot. Mexican onyx has, however, the banded

structure of quartz onyx and it is in allusion to this undoubtedly that

the name has been applied. A sardonyx upon which Queen Elizabeth’s

portrait was cut constituted the stone of the famous ring which she gave

the Earl of Essex as a pledge of her friendship. It will be remembered

that when the Earl was sentenced to death he sent this ring to his

cousin, Lady Scroop, to deliver to Elizabeth. The messenger by mistake

gave it to Lady Scroop’s sister, the Countess Nottingham, who being an

enemy of the Earl’s did not deliver it to the Queen and the Earl was

executed. On her deathbed the Countess confessed her crime to the Queen,

who was so infuriated that she shook her, saying “God may forgive you,

but I cannot.” The onyx is the emblem of conjugal felicity and by some

is made the “birth stone” of the month of July. It is one of the stones

prescribed for the ephod of the Jewish High Priest.

The sardonyx was supposed by the ancients to be a different stone from

the onyx. To it was ascribed the property of conferring eloquence upon

its wearer. It is mentioned in Revelations as one of the stones forming

the foundations of the Holy City. Onyx and sardonyx which come from the

Orient are esteemed of much higher value in trade at the present time

than those prepared in Germany. There seems to be no good reason for

this, however, as the latter can be so skillfully made that it is

impossible to distinguish them from the Oriental stones.

Jasper is a name which includes in general nearly all varieties of

impure opaque colored crypto-crystalline quartz. In color it may be red,

yellow, green, brown, bluish and black. To many of the pebbles found on

almost any sea or lake shore or in the beds of streams the name jasper

may properly be applied. If it occurs banded, that is, in stripes of

different colors, it is known as ribbon jasper. The different colors of

jasper are due to the different impurities it contains. These may be

clay, iron oxides or organic matter and at times reach a quantity as

high as twenty per cent. The color often varies irregularly in a single

stone, giving different effects and sometimes imitating paintings.

Jasper which can be used in the arts is very widely distributed. Good

red jasper is obtained in Breisgau and near Marburg in Germany. Much of

the brown jasper comes from Egypt. What is known as “Sioux Falls jasper”

from Sioux Falls, South Dakota, is chiefly of a brown color. This stone

was highly prized by the Indians for its color and is the “jasper”

referred to by Longfellow in Hiawatha:

“At the doorway of his wigwam

Sat the ancient Arrow-maker

In the land of the Dacotahs,

Making arrow-heads of jasper

Arrow-heads of chalcedony.”

The yellow jasper used for mosaics comes chiefly from Sicily, but as

good could be obtained in many places in our own country. The green

jasper of the present time is obtained chiefly in the Urals and is to a

considerable extent worked there into ornamental pieces. The Chinese

prize green jasper highly, the seal of the Emperor being made from it.

Some jasper of a bluish shade is found in Nature, but that of a deep

blue tinge is always artificially colored by Prussian blue. It is then

sometimes known as “false lapis,” that is, false lapis lazuli. Ribbon

jasper is found in Saxony, but chiefly comes from the Urals. The

qualities which make jasper of use in the arts are its color, opacity

and capacity for taking a polish. At the present time it is not much

used except for mosaic work and for small boxes, vases and dishes. The

ancients, however, prized it highly and used it extensively. It is one

of the stones prescribed in the Book of Exodus to be worn in the ephod

of the High Priest and also forms one of the gates of the Holy City as

described by St. John in Revelations. It is probable that the jasper

referred to in these instances was of a dark green color, as this was

the tint most prized in early times. Green jasper was also called

emerald in some instances. The banded varieties were much used for

cameos, specimens of which are still extant. By taking advantage of the

colors of the different layers, colored objects were made, such as one

which shows the head of a warrior in red, his helmet green and

breastplate yellow.

Basanite is also known as Lydian stone or touchstone on account of its

use for trying the purity of metals. Its value for this purpose depends

on its hardness, peculiar grain and black color. Different alloys of

gold give different colors on the stone which one soon learns to

recognize, and jewelers become very skillful in judging of the fineness

of gold by this test. Also if an object is plated, by giving it a few

strokes on the stone the different color of the gold and base will be

revealed. It is simply a black variety of crypto-crystalline quartz,

differing from jasper in being tougher and of finer grain and from

hornstone in not being splintery.

Flint is likewise an opaque quartz of dull color. It differs from jasper

in breaking with a deeply conchoidal fracture and a sharp cutting edge.

It is also often slightly transparent and has a somewhat glassy luster.

These properties have led to its extensive use by the Indians and by

nearly all primitive peoples for the manufacture of weapons and

implements. Hornstone is more brittle than flint and has a splintery

rather than a conchoidal fracture. A number of other subvarieties of

crypto-crystalline quartz occur, but they are not important.

Oliver Cummings Farrington.