Indonesia Natural Stone Source

Genta Works Website Review

Genta Works provides a number of Natural Stone products such as Mosaic Tiles, Stone Sinks, Marble Tiles, Stone Crafts, Pebbles, Wall Cladding, Tumble Marbles. Most of their products look very rough and could not be considered as a top class stone finished. However, you may get a good bargain, if you do not need the exquisite finish of stone product, as it brings down to lower price.

:: check out the site - http://www.gentaworks.com/ ::

What is Stone?

What is stone? The Oxford English Dictionary defines stone as "A piece of rock or hard mineral substance (other than metal), of small to moderate size". One of the most commonly used terms related to geology it derives from stan (Old English) and steinn (Old Norse). In the Gaelic it is clach.

The formation of sedimentary rocks was described in 1802, by Professor John Playfair, uncle to architect William, and friend of James Hutton, founder of modern geology. The notable 19th century Scottish geologist Sir Archibald Geikie eloquently commented on the process of transition from unconsolidated sediment to sedimentary rock: "If you take a quantity of mud, and place it under a weight which will squeeze the water out of it, you will find that it gets firmer. You can thus harden it by pressure. Again, if you place some sand under water which has been saturated with lime or iron, or with some other mineral that can be dissolved in water, you will notice that as the water slowly evaporates it deposits its dissolved material round the grains of sand and binds them together. Were you to continue this process long enough, adding more of the same kind of water as evaporation went on, you would convert the loose sand into a solid stone."

This is essentially the process of lithification (derived from the Greek word lithos – a rock). Thus in a sedimentary basin through compaction by the weight of overlying strata and by cementation by mineralised fluids so sedimentary rocks are formed. In contrast, igneous rocks are usually consolidated by crystallization of minerals from molten material either within the earth’s crust (e.g. granites) or at the surface (e.g. basalt lavas). As their name suggests metamorphic rocks have been transformed (recrystallised) from the original rock by a combination of heat and pressure. In these circumstances, new minerals sometimes form.

Choosing the Right Stone

As building material, stone has several positive features:
• It is easily available
• When correctly processed, stone is a stable, almost eternal material.
• It is non-flammable.
• Its appearance is natural and unique.

To enhance these features, the aesthetical and mechanical properties that determine the possible uses of a rock type must be understood in the planning phase. Only then can a long-lasting, beautiful result be achieved. There are couple of things to look at:

Outer Appearance
The outer appearance of rock types varies. Stone is a natural product. The texture and colouring of the material vary, contributing to its unique appearance. Surface treatments can either enhance or fade the surface colours and patterns.

Mechanical Properties
During dimensioning and attachment methods management, the mechanical properties of stone slabs must be taken into consideration. The weather resistance and susceptibility to discolouring are also estimated. The European Committee for Standardisation, CEN, has defined standard methods for the testing of mechanical properties. These are some descriptions for types of Mechanical Properties:

Water absorption
Water absorption is measured as mass percentage of dry weight. The water absorption of porous rocks is greater than that of dense rock types. As a result, porous rocks are susceptible to discolouring and have poor frost resistance. The values for dense rock types vary between 0.1 and 0.5 mass percents. The absorption value for porous rock types may exceed 20. A rock will have good frost resistance, when its water absorption is less than 0.5 mass percents.

Hardness
Measured by scratching the surface with mineral. Values are reported in Mohs' hardness, a scale of 1 to 10 Mohs, where the hardest rock will receive the value 10. This value can be used in estimating durability and persistence.

Thermal transformations
Thermal transformations are changes in volume that are caused by temperature changes. These properties are necessary in evaluating the need for expansion joints in structures. The thermal transformations of natural stone vary between 0.2 - 0.9 * 10^-5/C, and are less than with most building materials.

Humidity transformations
Humidity transformations are changes in volume that are caused by changes in humidity. Only the thin marble tiles have been shown to respond notably to changes in humidity. Marble tiles tend to bend unevenly when they get wet. For other rock types, this property bears little significance.

Abrasion resistance
Abrasion resistance must be considered when selecting the surface treatment, if the abrasion burden is significant. The European Union has issued a standard for abrasion resistance.

Breaking around a fixing point
The likelihood of stone breaking around a fixing point depends on several factors: the size of the stone slab, the quality and quantity of fixing points, and the hardness of the rock type. The sufficient value of 2 - 5 kN can usually be attained, when the slab is 30 mm thick.

Weather resistance
In the long run, weather resistance plays an important role in the durability and appearance of facades. Exposure to the climate and weather conditions may result in discolouring or colour changes, diminished polish, chemical and mechanical weathering, and in bent stone slabs. Different rocks have different weather resistance properties.

Igneous rocks (e.g. granite)
In igneous rocks, exposure to climate and weather conditions causes mainly surface discolouring. Surfaces with bush hammer finish are easily discoloured, but on a polished surface discolouring is close to non-existent.

Limestones and Marbles
Alkaline rock loses its shine and strength in acidic urban atmosphere. In only ten years, exposure to acid rains will result in severe weathering and cause limestone and marble to become brittle.

Choosing the Stone
Stone Type/Property
Granite - Marble - Calcite - Limestone density "a" - Limestone density "b" - Sandstone - Schists

Density min kN/m
25,6 - 25,9 - 17,6 - 25,6 - 22,4 - n/a

Water absorption max (mass percent)
0,4 - 0,75- 12 ,0 - 3,0 - 20,0 - 0,25

Compressive strength/Compression resistance min (MPa)
130,0 - 52,0 - 12,4 - 55,2 - 13,8 - n/a

Abrasion resistance min
10,0 - 10,0 - 10,0 - 8,0 - 8,0

Availability
It is advisable to determine the availability of a rock type before making the final selection. While planning, it is wise to have a few alternatives before confirming the order of the material. The project schedule should also be planned only after receiving confirmation on the availability of the chosen rock. Depending on the degree of processing, it may take 2 to 6 months before the ordered slabs are ready to be assembled.

Slate Information

Slate is formed through metamorphism, a process in which the tiny elements that make up a rock are pushed closer together to form a crystalline structure, also known as recrystallization of the stone. This all occurs while the stone is in a solid state, and the materials that make up the stone are not changed, they are merely repositioned to be closer to one another in a crystal pattern. Metamorphism can be caused by heat or pressure. The materials which undergo this transformation to form slate are generally a shale type sedimentary rock.

Slate forms in layers that easily cleave off in thin lines, generally known as Slaty Cleavage. During formation the original sedimentary rocks are forced down into these plains due to immense pressure. The resulting slate can be comprised of many different beds of sedimentary rock, all of which are now reoriented in the same direction.

While slate is generally a grey or grey-blue color, it can also have multicolored effects in its surface. These come from the various different beds of sedimentary rock from which it is derived, often making this material a contrast of hues.

Slate is most commonly used for roofing because it can be sliced into thin layers. It is also very popular in flooring, countertops, and architectural applications, due to its durability, its natural beauty, and it’s relatively low cost. Its clefted surface makes it slip resistant, causing it to be popular in kitchens, bathrooms, and restaurants, as well as public hallways and other high traffic areas. It is also used in decorative home furnishing, fish tanks, and even in novel accessories such as board games.

Slate is found naturally in mountains. When it is quarried, it is usually done so in large blocks known as slabs. These blocks are then chopped up into smaller slabs for distribution. The size of the slab they can make is dependent on the relative strength of the type of slate. The inherent layering of this material makes some rather large sizes difficult to maintain and keep from cracking.

In stores, slate is generally available in tiles of various sizes including 16X16, 12X12, 8X8 as well as in slabs of various sizes, usually running to about 80 inches in length. Installations are generally done with mortar backing to even out varying thicknesses. Then grout lines are run along the joints of the stones. It is important to adequately seal and protect all tiles before grouting them.