a. An isometric mineral, ZnS , with Zn replaced by Fe with minor Mn, As,
and Cd; trimorphous with wurtzite and matraite; perfect dodecahedral
cleavage; resinous to adamantine; occurs with galena in veins and
irregular replacement in limestone; a source of zinc. Syn:blende;
zinc blende; jack; blackjack; steel jack; false galena; pseudogalena;
mock ore; mock lead. See also:beta zinc sulfide
b. The mineral group coloradoite, hawleyite, metacinnabar, sphalerite,
stilleite, and tiemannite.
See:titanite
An open crystal form of two nonparallel faces which intersect two or three
crystallographic axes. CF:dome; disphenoid.
A wedgelike igneous intrusion, partly concordant and partly discordant.
AGI
See:manganite
A fernlike tree of the coal forest characterized by round-lobed pinnules
that are contracted at the base. See also:Neuropteris
See:cockade ore
A general term applied to rocks made up of spherules. It includes such
textures as oolitic, pisolitic, spherulitic, variolitic, orbicular, etc.
Johannsen
A brick or concrete seal or stopping built into a roadway to close off an
area against water. The convex surface is from the water side of the
roadway. The construction is built well into the ground and all crevices
cemented. Nelson
A function frequently used when fitting mathematical models to
experimental variograms, often in combination with a nugget model.
A seismic wave propagated from a point source whose front surfaces are
concentric spheres. AGI
Spherical surface that a given portion of a seismic impulse (in an
isotropic medium) occupies at any particular time. AGI
a. The preferred spelling for sphaerite. English
b. Spherical grains, including ovulite with concentric structure and
spherulite with radial structure. Spencer, 2
See:sphaerocobaltite
A homogeneous spherulite formed of minute crystals branching outward from
the center. See also:spherulite
In general, any figure differing but little from a sphere. In geodesy, a
mathematical figure closely approaching the geoid in form and size, and
used as a surface of reference for geodetic surveys.
a. Having the shape of a spheroid. AGI
b. Composed of spherulites. AGI
c. Said of the texture of a rock composed of numerous spherulites.
AGI
A series of concentric and spheroidal or ellipsoidal cracks produced about
compact nuclei in fine-grained, homogeneous rocks. CF:exfoliation;
spheroidal weathering. Syn:spheroidal jointing