Carving rock by indenting sharp objects into the surface under an impact force has been a favored method of fragmentation for millenia . However, as rock gets harder the lifetime of these sharp tools becomes short and, in a compromise hardened bits of rounder contour have become more common, particularly when driven by mechanical power. To better understand the behavior of these newer generatio...

Use of jet cavitation, however, occurs through an exit nozzle whose diameter can be changed, thereby changing volume with changing velocity. The results of such a change is shown to tie cavitation damage more powerfully to volume flow than to velocity. A specific example is in cavitation erosion of a high strength igneous rock which remained virtually undamaged at 70 MPa driving pressure but wa...

Findings of coesite and microdiamond in metamorphic rocks of supracrustal protolith led to the recognition of continental subduction to mantle depths. The crust-mantle interaction is expected to take place during subduction of the continental crust beneath the subcontinental lithospheric mantle wedge. This is recorded by postcollisional mafic igneous rocks in the Dabie-Sulu orogenic belt and it...

The composition of the silicate portion of Martian regolith fines indicates derivation of the fines from mafic to ultramafic igneous rocks, probably rich in pyroxene. Rock types similar in chemical and mineralogical composition include terrestrial Archean basalts and certain achondrite meteorites. If these igneous rocks weathered nearly isochemically, the nontronitic clays proposed earlier as a...

The rare earth elements (REE) are composed of the Lanthanide Series of 15 elements with atomic numbers (57) through (71) and yttrium (39). Because of their geochemical behavior, REE rarely form their own minerals and more commonly are found incorporated within the structure of other minerals. There is growing concern over the economical availability of REE because of their diverse and expanding...