Marble, formed from limestone with heat and pressure over years in the earth's crust. These pressure or forces cause the limestone to change in texture and makeup. The process is called re-crystallization. Fossilized materials in the limestone, along with its original carbonate minerals, re-crystallize and form large, coarse grains of calcite. Impurities present in the limestone during the re-crystallization period affect the mineral composition of the marble which is formed. At relatively low temperatures, silica impurities in the carbonate minerals form masses of chert or crystals of quartz. At higher temperatures, the silica reacts with the carbonates to produce dropsied and forsterite. At a very high temperatures, rarer calcium minerals, such as larnite, monticellite, and rankinite, forms in the marble. If water is present, serpentine, talc, and certain other hydrous minerals may be produced. The presence of iron, alumina, and silica may result in the formation of hematite and magnetite.

The minerals that result from impurities give marble a wide variety of colors. The purest calcite marble is white in color. Marble containing hematite are reddish in color. Marble that has limonite is yellow, and marble with serpentine is green in color.

Marble does not split easily into sheets of equal size and must be mined with care. The rock may shatter if explosives are used. Blocks of marble are mined with channeling machines, which cut grooves and holes in the rock. Miners outline a block of marble with rows of grooves and holes. They then drive wedges into the openings and separate the block from the surrounding rock. The blocks are cut with saws to the desired shape and size.

Different Types of Marbles

White Marble
White marble is available in Makrana ( District Nagaur ) in huge quantity, which is often called Makrana stone in laymen term. The marble deposit of Makrana is about 12 km. in length and 1.6 km. in length and 1.6 km. in width. Well known deposits are found in Kumari, Dungari, Bhermata Y Chancer area. The deposit of Chancer area is considered to be the finest one and quarries of this area have gone upto a considerable depth of 15 to 60 meters. Now a days, because of deep mining and other factors, mining in Makrana area has become uneconomical. Further, good quality material has also been exhausted. Hence the need for developing new areas where marble is available, close to surface was felt. Soon in Rajnagar (Udaipur District) huge deposit of white marble was discovered by the State Department of Mines & Geology.

Although marble deposit in Udaipur district are known since long back when palaces and monuments in and around Udaipur were built with local marble but in recent years this district has received more attention and mining activity in this district has developed rapidly. In Udaipur district white marble is mainly available in Rajnagar, Amet, Saprao, Marchana, Agaria, Parvati etc. Apart from Udaipur district white marble in huge quantity is also available in Tripura Sundri (District Banswara). This marble is fine grained and has varities which are pure white or that have pinkish or yellowish shades. Some varieties resemble to Italian Marble.

Pink Marble
This Babarmal area of Udaipur district is the only main producer of Pink Marble in the state. The area is situated at 25 km South of Udaipur city on Jaisamand road 100 meters marble is some what hard, hence require more time in cutting. Besides this, small quantity of pinkish marble is also in width .. This belt is about 5.20 km in length and 30 to found in Makrana and Abu Road area.

Green Marble
Green marble is found in keshriya ji about 60 km south of Udaipur. There is great craze of this marble because it has white jali with light or dark green base which shines very good after polishing Block recovery is very little as lot of cracks are found and hence it is generally used for making chips and crazy. This variety is actually serpentine rock but in trade it is known as green marble.

Other Marble
Others types of marble are found in different parts of Rajasthan. Yellow marble which actually shally lime stone and takes good polish is available in Jaisalmer. Marble deposits of Bhainsalana in Jaipur district is known for its black strips. In Pali, Marble deposits exists near Bar and Sendra. It is mainly pink colored with various shade and strips . Different types of marble is also found in Ajmer, Jahazpur, Bundi. etc. but the deposits are very small. In Rajasthan mining is mostly done by open cast method. Only in Makrana at Chancer area underground mining method has been adopted where it has been mines upto 100 meters depth but, the deposit is of spotless white marble. Mining does not come under the head of industry hence it is deprived of the benefits available to an industry, Moreover, financing institutions are also reluctant to finance the mines. Therefore, mechanized mining is not developing rapidly. To increase the marble production it becomes necessary to mechanize the mine and minimize the use of explosives to reduce the breakage so that it can cope-up with the increasing demand of marble blocks by the diamond gang saw and other conventional machines.

Stone Marbles

Calcareous Stone Marbles
The very earliest marbles were made of stone. Stone was used for marbles by the Roman and Greek civilizations as well as even earlier cultures. Alabaster and marble spheres were used in England from around the fifteenth century. Small stone spheres were first produced in large quantity in Germany with the aid of water mills as early as the seventeenth century. Most of the mills were located in the mountain streams of the Alps, particularly near Berchtesgaden, using marble from local quarries to produce a moderatequantity. It wasn't until the eighteenth and nineteenth centuries, that great quantities of marbles were produced by larger mills. The largest concentration of these mills was in Saxony, Germany. An important marble-producing town was the city of Coburg.

The workers broke the calcareous stone into 1" suqare blocks with small hammers, 100-200 of which were then placed in a mill to be ground. A stationary flat stone slab with concentric grooves cut into it was used to placed the stone blocks onto. Above the slab was a large round sectioon of oak the same diameter as the slab, partially resting upon it. Water ran between the two blocks, and the oak block rotated. In about fifteen minutes, the marbles would be ground and ready for public sale. About 60,000 marbles could be turned out by one mill in a week.

Along the mountain streams in the south Thuringer woods, handmade glass marbles were produced. Near the end of the nineteenth century, this province became famous as the leading producer of handmade glass marbles in the world. Prior to that, limestone marbles were produced in Thuringer. The Deutchess Spiel zeugmuseum (German Toy Museum) at Sonneberg, Thuringen,has information about the production of these marbles in the Sonneberg area, and in it's collection it has an old mill from Almbachklamm in the vicinity of Berchtesgaden. The marble industry was practiced in the Sonneberg area probably since the Thirty Years' War, and reached its first heyday around 1740 when a small group of emigrants from Salzburg perfected the technique of marble production. A second time of peak production was the period after the mid-nineteenth century when German exporting rose appreciably. In the 1870's the toy industry burgeoned, most of the marble miners of Thuringen turned to this healthier industry, the mines falling into disrepair.

Agates
Agates also came from Germany, where large agate mills and quarries could be found on the Nahe River at Oberstein. The smaller pieces of stone were put to good use by being made into marbles by skilled craftsmen, mainly for export to the American market. Workmen chipped the pieces nearly round with a hammer, then wore down the edges on the surface of a large grindstone. Production of marbles reached a peak between 1880 and 1890, when marbles were being ground in Idar-Oberstein and in Bundenbacj, a small town in the same area. Marbles were also quite popular in Africa at this time, a great portion being exported there.

Marbles produced in the greatest volume, and most important to the trade, were made of banded agate. However, the grinders in this region also produced marbles of rose quartz, tigereye, and other semiprecious stones. Marbles were used to decorate large hat pins, and merchants called marbles "klickers." Agate marbles are still produced today in Idar-Oberstein. The agates come in many different colors, but most can be distinguished by the bands of different colors which circle the marbles. The bands usually alternate red and white or brown and white, although there is almost an infinite variety of shades which can be found. Bands may increase in width as they near the ends of the marble to form a white spot surrounded by a red band, which gives the marble the appearance of an eyeball.

Some agate marbles show a long narrow elliptical pattern, pointed at both ends, Some bands are ,less well-defined instead of a band, giving the marble the appearance of having a drawn-out toothy grin. Some bands are less well-defined, making the marbles more translucent. A good way to tell if a marble without distant markings is agate or imitation is to hold it up to the light. Most of the glass imitation agates are opaque. Also, the red and white markings on imitation agates aren't in regular bands, but irregular shaped swirls. Gray agate marbles also exist, but usually contain bands of white or lighter gray.

You may encounter a marble which appears to be agate but is some color which no expectable agate would be found in, as green. Agate is one of the semiprecious stones which can be colored either by dyeing or by heating, the finished product lovely looking with the green color penetrating through the entire marble. This green coloring actually replaces the natural color previously present. These marbles then have light green and dark green alternating bands, and as translucent as before.

Agate belongs to a type of quartz called cryptocrystalline, consisting of microscopic crystals. Regular quartz has large crystals. One big section of this group of quartz, known as chalcedony, contains agate, used for making marbles Agate has a banded or irregular, variegated appearance. Oxny is an agate with even parallel layers of black and white or brown and white; sardonyx of carnelian (red) and white

Other Stone Marbles
Tigereye, golden quartz with inclusions of a type of asbestos which often has blue fibers, has also been used to make marbles in Germany. This stone is not mined in Germany itself, but comes from such unlikely places as Grinqualand West, South Africa. Tigereye marbles appear to be dark brown in color with bright golden bands circling them. Rose quartz marbles were also made by the early German craftsmen, and are fairly easy to identify by their pink color. Most pieces of rose quartz of any size are fractured inside, since it is quite hard to get a piece of this material in its natural state which is perfect. Bloodstone, a form of green chalcedony with red spots scattered through it resembling drops of blood, was occasionally used for marble-making. The green color of this stone is often quite dark being almost a blue-green in shade. With this background, the small specks of red contrast quite brightly. Very few of these marbles of those of rose quartz were produced, making both types quite rare. Marbles have also been made of Petoskey stone, a type of fossilized coral, or to be more specific it is a calcite replaced coral of the genus Hexagonaria. The genus name Hexagonaria refers to the fact that the coral cells of this group are six sided. The fossil stones display a pattern of little hexagons one next to the other across the surface, visible within marbles made from this stone. The name petoskey comes from the city of Petoskey, Michigan, and these stones are only found along Lake Michigan from Petoskey to Charlevoix, with the exception of some similar types which are found in southern Iowa and southern Indiana.

Goldstone Marbles
Goldstone marbles are actually glass. Goldstone is actually gold aventurine, which is a glass containing particle of copper. Green aventurine contains chromic oxide, and reddish aventurine contains ferric oxide. Aventurine can also refer to translucent quartz which is spangled throughout with scales of mica or some other mineral. The marbles, however, are the glass with the copper flecks

Modern Stone Marbles
Agates are still produced today in Germany and sold in the U.S. There is no way to tell the modern agates from the antiques made a century ago. Take caution when buying agate marbles, especially if many in good condition are for sale. The grinding and polishing process of agate to make marbles is still time consuming and expensive making prices of the modern agates almost as high as the older ones.

Sphere machines which can form large marbles of different types of rocks are also becoming more popular among rock hounds. Most of these spheres are fairly large, certainly larger than normal agate marbles. Today, large alabaster spheres in a variety of pretty colors made abroad are sold in the gift sections of many U. S. stores. These have little value as a collector's item, rather as a home decoration. Rose quartz marbles are fairly new to the marble market.