Mineral Resources Potential - Geothermal Resources

Industrial Minerals 161
called p omb is mixed with lime to form a light-weight, smooth,
plaster-like cbncrete.
Pumice deposits in Ethiopia
Large resources of volcanic scoria and pumice have accumulated
within and along the margins of the rift valley. These resources can
be used in soil moisture conservation techniques, called rock
mulching. Experiences from other parts of the world, especially the
Canary Islmdq have shown that rock mulch can considerably
reduce evaporation from soil surfaces.
Pumice occurs in several localities of the Rift Valley as
recent shore sediment of lakes and also as older lacustrine
sediments. Pumice =ewes are located near Nazareth railway
station and in the Mojo stxea. Other deposits occur as shore
sediments at Debrezeit, Langano, Awassa and other Rift Valley
Lakes, Rock mulch field experiments using local scoria and
pumice resources fiom near Naareth were carried out in the
wework of the Ethiopia-Canada agrogeology project (Woldeab
ei al., 1 994). The results of field experiments illustrated the effects
of scoria and pumice mulches in the Rift Valley of Ethiopia. The
application of 3 to 5 crn scoria or pumice mulch on top of the soil
swfim resulted in effective soil moisture conservation, as well as
grain yield increase of maize by as much as 4 he (Wold& et
al., 1994). The main constraints to this system are availability of
mulching materids in the close vicinity to soils with moisture
stress, and economics.
4.21 Natural zeolites
Zeolites are the aluminosilicate members of the family of
microporous solids known as "molecular sieves". Zeolites are
widely used as ion-exchange beds in domestic and commercial
water purification, softening, and other applications. In chemistry,
zeolites are used to separate molecules (only molecules of certain