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.
Historical Examples. 1  A lintel, consisting of a single stone, some two tons' weight, was supported by the protruding jambs. 2  On the lintel of the gate and in the lock dust lies accumulated. 3  At the door, in the middle of the end of the street, he paused and struck on the lintel three times with his gun-butt.