Most travertine will have some degree of holes which are generally filled with a cementitious or epoxy filler and then honed to give it a smooth, uniform surface. The amount of "filler" will dictate the grade and value of the stone. The less filler there is the higher the grade and cost. However, the holes do not have to be filled. In fact, unfilled travertine is quite beautiful, creating a more rustic feel and look to the space. Unfilled travertine is also a favorite for exterior cladding on buildings. If you really want to get fancy, you can also purchase honed and polished travertine.
Travertine results from hot spring water percolating up through underground limestone. When the water evaporates, it leaves behind layers of dissolved limestone and other minerals, giving it its banded appearance. The characteristic holes in travertine are the result of trapped gas bubbles; as the gas escapes, crystals form in the cavities. Travertine is generally light-colored beiges and tans, although there are some beautiful, colored travertine boasting red, silver, amber, gold, and many other colors. These colors are actually caused by minerals dissolved by hot water underground.
Granite is an important structural and ornamental stone, and due to its high compressive strength and durability, it is used for massive structural work. Fine-grained granite is employed for ornamental and monumental work as well as for inscription purposes. It is the hardest of structural stones. Its mineral-rich colors, the hardness and density, make it an ideal choice for flooring, counter tops, vanities as well as exterior applications. A broad range of elegant patterns and colors makes granite the most versatile and durable of all stones. It is also the most "maintenance free" of all stones.
Granite is composed of quartz, feldspars and micas, as well as traces of a wide variety of other minerals. These minerals contribute to the color and texture of the various granites. Crystal size is somewhat determined by the rate at which the granite cools: the slower the cooling process, the larger the crystals grow. Faster cooling produces fine-grained granites. Granites get their wonderful variety of colors and patterns from minerals that are melted into the liquid mass as it is formed.
Marbles are formed from limestone or dolomite that has undergone enough heat and pressure to get metamorphosized into a crystalline structure. This metamorphosis takes place when the weight of overlying material, pressure from crystal collisions and heat from the earth's core generate temperatures in excess of 1800ºF. It has an interlocking or mosaic texture composed of crystalline grain of calcite, dolomite or both. Texture of marble depends on the form, size and uniformity of grains. The chemical constituents of marble determine the color of the marble. Generally calcite and dolomite marbles are of pure white color. Variations of whiteness of pure marbles are due to the mixture of foreign substances. Such impurities form bands, streaks and clouds. Black and grayish shades are due to graphite; pinks, reds are mainly due to the presence of manganese oxides or hematite.
Onyx is very similar to agate and formed from quartz. With cryptocrystalline structure and translucent property, onyx is one of the more popular precious gemstones. Onyx is generally formed from layered deposits in warm springs and limestone caves. Re-deposits are created by the water flowing over existing limestone which produce fine, grainy structures and form crystals. These re-deposit crystals have been fusing together for millions of years to form translucent layers which in turn form the unique natural stone onyx.
Onyx is naturally beautiful and translucent with lines of contrasting colors running throughout giving it its unique color characteristics. Onyx tends to be more crystalline, strongly banded and colored in browns, yellows, golds, reds, and greens. The colors are soft, yet boldly opulent. Fireplaces, bar tops and backsplashes are some appropriate uses for it. The translucent qualities of onyx can be leveraged by positioning the stone in front of a light source. This back-lit masterpiece is not only gorgeous but will also be the topic of interesting conversations.
The vibrant colors and unique texture makes slates appropriate for interior as well as exterior applications. Slate is formed of compressed layers of sediments formed under ocean. Slate is a regionally metamorphosized, argillaceous rock, that has developed but has suffered re-crystallization, and compressed into a dense stone made up of quartz, iolite, mica and calcite. Because it is formed in layers, it can easily be split to expose beautifully textured surfaces. The usual colors of slates are earthy (various shades and mixes of browns, beiges, yellows), black, dark-grays, and greenish-gray but shades of pinks, purples and copper are also found. They usually exhibit a lot of variations amongst the pieces quarried from the same pit. Slates, depending on their individual hardness, are used for flooring, cladding and landscaping.
The muted tones of limestone are perfect for today's more casual and comfortable lifestyles. Generally these soft beiges and tans, either polished or honed, is appropriate for bathrooms, fireplaces, counters and less-traveled flooring where a more informal decor is desired.
Limestone is sedimentary rock that forms at the bottom of lakes and seas, as silt and organic matter settle to the bottom. As more and more layers build up over millions of years, adding more and more weight, the heat and pressure cause chemical reactions to take place, hardening the sediments into solid stone.
Quartzite's are very similar to slates, but with higher content of Quartz in them, which gives them, a sparkling texture. They are so close to slates that usually they are referred to as quartzitic-slates. Just like slates, they are used for various applications depending on their hardness.