The pore spaces (known as vesicles) in pumice are a clue to how it forms. The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure.umice is produced in two forms: rock pumice and pumicite. Pumicite is a name given to very fine grained pumice (less than 4 millimeters in diameter down to submillimeter sizes).
Post and lintel construction is recognized by its simple vertical and horizontal design, in which a pair of vertical supports are set in the ground or a foundation, and a horizontal structure is balanced on top of them.
1 2. LINTELS â¢ Introduction â¢ Classification of lintels ARCHES â¢ Arches: Terms to be used â¢ Stability of an arch â¢ Classification of an arches 2. 2  3. Lintels ï¶ Introduction ï¶ Classification of lintels 3.3  4. Introduction ï¶ A lintel is defined as a horizontal structural member which is placed across the opening. 4.4  5. 5. 5  6. 15)Spandril:-This is the triangular walling enclosed by the extrados of the arch, a horizontal line from the crown of the arch and perpendicular line from the springing of the outer curves. 23. 2  24. ï¶ ï¶ 3  EVERY ELEMENT OF ARCH REMAINS IN COMPRESSION. 4  An arches fail due to:1)Crushing of the masonry.