Xim Lava Pumice Pob Zeb yog tsim thaum super-heated, pob zeb pressurized heev yog violently ntawm ib lub roob hluav taws.

Qhov txawv foamy configuration ntawm pumice tshwm sim
vim hais tias ntawm simultaneous ceev txias thiab sai depressurization. Lub depressurization tsim ua npuas los ntawm kev txo cov dej ntawm cov roj (xws li dej thiab CO2)
uas yog yaj ua lava, ua rau cov roj cua kom sai exsolve (xws li cov npuas ntawm CO2 uas tshwm sim thaum lub qhov dej haus tau qhib). Lub simultaneous txias thiab depressurization freezes lub npuas nyob rau hauv ib tug Matrix. Cov dej nyob hauv dej txias sai thiab cov ntim loj ntawm pumice tsim tau yog kev thauj khoom thauj khoom thauj khoom thauj nkoj.

Pumice yog li ntawm microvesicular iav pyroclastic nrog cov thin heev, txhais kom pom cov phab ntsa ntawm extrusive igneous pob zeb. Nws yog feem ntau, tab sis tsis yog yam tshwj xeeb
ntawm silicic los yog felsic rau intermediate nyob rau hauv cov koog (xws li, rhyolitic, dacitic, andesite, pantellerite, phonolite, trachyte), tab sis basaltic thiab lwm yam compositions paub.

Pumice feem ntau yog xim daj ntseg, xws li dawb, qab zib, xiav lossis grey, ntsuab-xim av los yog dub. Nws cov ntaub ntawv thaum volcanic gases exsolving los ntawm cov nplaum magma daim npuas uas nyob twj ywm hauv lub magcous magma li nws cools rau iav. Pumice yog ib qho khoom siv tawg rog tawg (plinian thiab qhov tsis ua haujlwm) thiab feem ntau cov aav zones nyob rau sab saud ntawm cov pob zeb silicic. Pumice muaj porosity ntawm 64-85% ntawm ntim thiab nws floats ntawm dej, tejzaum nws xyoo, txog thaum nws yog nws tus dej eventuallyged thiab ntxuav.

Siv

Pumice yog ib qho nyhav me me, ntxeem tau thiab ntxhib khoom thiab nws tau siv rau centuries hauv kev tsim kho thiab kev lag luam kev zoo nkauj thiab cov tshuaj thaum ntxov.
Nws kuj yog siv raws li tus txheeb ze, tshwj xeeb tshaj yog nyob rau hauv polishes, mem hluav erasers, thiab cov khoom ntawm pob zeb ntxuav-ntxuav. Pumice kuj tau siv nyob rau hauv phau ntawv ntxov ntxov ua kev lag luam los npaj npaj ntawv khoob thiab daim tawv khi. [22] Muaj qaug zog rau cov pumice, tshwj xeeb tshaj yog rau dej pom, cov tshuaj muaj kuab, kev sib tsoo, kev lag luam thiab kev ua haujlwm rau tsiaj txhu. Cov mineris ntawm cov pumice hauv cheeb tsam thaj chaw muaj kev thaj yeeb tau nyob hauv ntau qhov kev soj ntsuam tom qab qhov kev lag luam raug nres hauv Teb Chaws Asmeskas hauv Oregon, ntawm Rock Mesa nyob rau sab qaum teb ntawm peb cov viv ncaus Wilderness.