Monday, September 28, 2009

Chemical & Physical Properties of Granite

Chemical Properties

Granite is mainly composed of feldspar, quartz along with different other minerals in varying percentage, which are affirmed as follows:

Nominal chemical composition of a variety of oxides

Silica (SiO2) ---------------------- 70-77%
Alumina (Al2O3) ----------------- 11- 14%
Soda (Na2O) ------------------------ 3 – 5%
Potassium Oxide (P2O5) --------- 3 – 5%
Iron (FeO) ----------------------------- 1 – 3%
Iron (Fe2O3) -------------------------- 1-2%
Lime ----------------------------------- 1%
Magnesia (Mg0) ------------------------- .5 – 1%
Titina ---------------------------------- Less than 1 %( .38%)
Water (H2O) --------------------------- 0.03%

Physical Properties

In terms of granites physical properties, it is a unique material. These properties lend uniqueness to granite are:

Co-efficient of expansion :
The co-efficient of expansion for granite vary from 4.7x10-6 – 9.0x10-6(inches x inches).

Porosity/permeability :
Granite has almost negligible porosity range among 0.2 to 4%.

Variegation :
Granite shows constancy in color and texture.

Thermal Stability :
Granite is highly steady thermally, therefore shows no change with the change in temperature. It is impervious to weather from temperature and even from the air borne chemicals. Granite is the high confrontation to chemical erosion that makes it useful for making tanks to store highly caustic material.

Hardness :
It is the hardest building stone and hardness of it that lends it excellent wear.

Monday, September 21, 2009

Granite emitting Radiation:

New information about probable hazards of granite and stone countertops. Recent articles told countertops of granite emit unacceptable levels of radiation. "Allegations those granite countertops may produce dangerous levels of radon and radiation has been raised periodically over the past decade, mostly by makers and distributors of competing countertop resources. The Marble Institute of America has said such claim are "ludicrous" since although granite is known to contain uranium and other radioactive materials like thorium and potassium, the amounts in countertops are not sufficient to pose a health threat.

Health physicists and radiation experts agree that the majority granite countertops produce radiation and radon at extremely low levels. They say these emissions are unimportant compared with so-called background radiation that is continually raining down from outer space or seeping up from the earth's coating, not to mention emanate from manmade sources like X-rays, glowing watches and smoke detectors.

However, with increasing regularity in current months, the Environmental Protection Agency has been getting calls from radon inspectors as well as from concerned homeowners about granite countertops with radiation capacity several times on top of background levels. "We have been hearing from people all over the country concerned regarding high readings", said Lou Witt, a program analyst with the agency's Indoor Environments Division.

The Environmental Protection Agency recommends taking action if a radon gas level in the home exceeds 4 pico curies per liter of air (a calculate of radioactive emission); regarding the same risk for cancer as smoking a half a pack of cigarettes per day." Something to think about when choosing a counter top material...

Tuesday, September 1, 2009

Radiation in Granite is not dangerous:

From what we know, here are two ways in which countertops, tiles and other finish made of granite strength emit any level of radiation. The first is by the release of small amounts of the radioactive gas radon, which can be inhaled. The second is by straight radiation from the surface itself to the homeowner. In both cases, the radiation emit is from the same process – natural radioactive decay of one element into a new. Compare to other radiation sources in the home and outside, the risk to the homeowner from radioactivity emitted from a granite countertops or tiles is practically non-existent. In fact, the quantity of radon gas emitted by a granite countertop is a lesser amount of than one millionth of that already there in the household air from other sources.

Typical Contributions to Radon Content of Indoor Air (pCi/L)