Natural glass

Natural glasses are considered in terms of the time required to form them; the arrangement is: fulgurites; diaplectic glasses formed by impact; “normal glasses” formed by impact; volcanic glasses (terrestrial); and volcanic glasses (lunar). A progressive increase in homogeneity with time of formation is noted. A recurrent theme is the welding of small pieces by hot pressing. Tektites are considered last; they seem to resemble the slowly-formed glasses. Some tektites appear to have been formed by hot pressing. After clearing away some possible misunderstandings, the problem of tektite origin is submitted for consideration.