Pertaining to worldwide changes of sea level that affect all the oceans.
Eustatic changes may have various causes, but the changes dominant in the
last few million years were caused by additions of water to, or removal of
water from, the continental icecaps. AGI
Said of a stratified mineral deposit. CF:ataxic
Said of the banded structure of certain extrusive rocks, which results in
a streaked or blotched appearance. Also, said of a rock exhibiting such
structure, e.g., a eutaxite. The bands or lenses were originally ejected
as individual portions of magmas, were drawn out in a viscous state, and
formed a heterogeneous mass in response to welding. AGI
Said of a system consisting of two or more solid phases and a liquid whose
composition can be expressed in terms of positive quantities of the solid
phases, all coexisting at an (isobarically) invariant point, which is the
minimum melting temperature for the assemblage of solids. Addition or
removal of heat causes an increase or decrease, respectively, of the
proportion of liquid to solid phases, but does not change the temperature
of the system or the composition of any phases. See also:eutectoid
AGI
The lowest temperature at which a eutectic mixture will melt.
Syn:eutectic temperature
The ratio of solid phases crystallizing from the eutectic liquid at the
eutectic temperature. It is such as to yield a gross composition for the
crystal mixture that is identical with that of the liquid. It is most
frequently stated in terms of weight percent.
See:eutectic point
A pattern of intergrowth of two or more minerals, formed as they
coprecipitate during crystallization, e.g., the quartz and feldspar of
graphic granite. See also:exsolution texture
AGI
The equivalent of eutectic, when applied to a system all of whose
participating phases are crystalline. AGI
See:eutectic texture
In mineralogy, having distinct cleavage; cleaving readily. Fay
Said of a body of water characterized by a high level of plant nutrients,
with correspondingly high primary productivity. AGI
Peat rich in plant nutrients, nitrogen, potassium, phosphorus, and
calcium. Synonymous with calcareous peat. Tomkeieff
Radioactive radium mineral found in Brazil. Bennett
An orthorhombic mineral, (Y,Ca,Ce,U,La,Th)(Nb,Ta,Ti)2 O6 ;
forms a series with polycrase; brilliant to vitreous brown to black; in
pegmatites and placers commonly with monazite in Canada; Madagascar;
Norway; and Pennsylvania. A source of uranium, niobium, and tantalum.
Formerly called loranskite.
a. Pertaining to an environment of restricted circulation and stagnant or
anaerobic conditions, such as a fjord or a nearly isolated or silled basin
with toxic bottom waters. Also, pertaining to the material (such as black
organic sediments and hydrogen-sulfide muds) deposited in such an
environment or basin, and to the process of deposition of such material
(as in the Black Sea). AGI
b. Pertaining to a rock facies that includes black shales and graphitic
sediments of various kinds. Etymol: Greek euxenos, hospitable. AGI
To fix a valuation, but not to appraise.
The fixing of a evaluation, not an appraisal. Used in preference to the
word valuation which is often confused with appraisal.
An amorphous mineral, Al3 (PO4 )(OH)6 .6H2
O(?) ; may contain small amounts of uranium and thorium; associated with
limonite and allophane.
To convert into vapor. See also:evaporite
a. The process, also called vaporization, by which a substance passes from
the liquid or solid state to the vapor state. Limited by some to
vaporization of a liquid, in contrast to sublimation, the direct
vaporization of a solid. Also limited by some (e.g., hydrologists) to
vaporization that takes place below the boiling point of the liquid. The
opposite of condensation. AGI
b. The process by which a substance is converted from a liquid state into
a vapor. Specif., the conversion of a liquid into vapor in order to remove
it wholly or partly from a liquid of higher boiling point or from solids
dissolved in or mixed with it. CF:distillation; sublimation.