Perlite is an acid mineral of volcanic origin. In ancient geological eras, the lava quickly cooling off in the aquatic environment escaping from an undersea volcano contained water drops inside. It is these drops of water (2-5%) enclosed in frozen and weathered lava that are responsible for its specific properties.

The chemical composition of perlite is:

• SiO2 (65 75%),
• Al2O3 (10 18%),
• K2O + Na2O (6 9%),
• MgO + CaO (2 6%),
• Fe2O3 (1 5%).

Perlite is a form of natural glass. It is a chemically inert product with a pH of about 7.
The raw mass of raw perlite is from 2.23 to 2.40 kg / dm3, the bulk density is from 1.00 to 1.30 kg / dm3. Hardness 5.5 to 7.0 on the Mohs scale. Melting point 950 1300oC, refractive index 1.48 1.50. It is brittle and easily crumbles. Perlite extracted from the deposit is ground to the appropriate granulation and then introduced into the furnace at a temperature of 900 1000oC for a few seconds. Water droplets enclosed in grains produce water vapor with sufficient pressure to crush the material to the size of several dozen m to several mm. In parallel, the sintering process of volcanic glaze occurs, and usually empty and slightly irregular, glassy bubbles are formed inside. This process is called expansion (upset), and the resulting product with an off-white color - expanded perlite. The grain volume increases 5 to 20 times. Photo 1 below illustrates the way to reach the expanded perlite produced in ZGM "ZĘBIEC" SA - a piece of perlite ore (on the right of the photo) is ground in the mining plant for appropriate granulation into raw perlite (gray powder inside), and this is subjected to a process of expansion resulting in a white perlite (on the left side of the photo). Depending on the type of raw material and the method of expansion, different grain fractions are obtained, which are divided into classes. Perlite is characterized by a small spherical blow (pearls), resulting from stress during rapid cooling of the enamel. In addition to the pure white color, light gray and grayish shades also appear. It is characterized by wax to pearly gloss. It is transparent to translucent. Expanded perlite has a loose bulk density of 30 180 kg / m3. Expanded perlite is chemically inert, non-flammable, non-hygroscopic and has a constant volume. It is resistant to frost, moisture, pests and microorganisms, and also has excellent thermal insulation and soundproofing properties.

Application

• architecture
• Metallurgy
• Agriculture
• Ceramics
• Food industry
• Environmental Protection
• Other uses

Type of screen [mm]

• above 1.00 = max. thirty %
• below 0.20 = max. 40%