A vase of calcite, also dedicated by Entemena, has been found at Nippur.
Calcite of excellent quality is the commonest mineral.
The cells forming the limbs of the ectodermic folds secrete nodules of calcite, and these, fusing together, give rise to six (or twelve) vertical radial plates or septa.
The zone of the external surface of the mantle within the edge secretes a layer formed of prisms of calcite; the rest of the epithelium from this zone to the apex secretes the inner layer of the shell, composed of successive laminae; this is the nacreous layer, and in certain species has a commercial value as nacre or mother-of-pearl.
A ring-shaped plate of calcite, secreted by the ectoderm, is then formed, lying between the embryo and the surface of attachment.
Heulandite, with thomsonite, stilbite, scolecite, calcite and chalcedony, occur as infilling minerals.
Many are found as minerals, the more important of such naturally occurring carbonates being cerussite (lead carbonate, PbC03), malachite and azurite (both basic copper carbonates), calamine (zinc carbonate, ZnCO 3), witherite (barium carbonate, BaCO 3), strontianite (strontium carbonate, SrC03), calcite (calcium carbonate, CaC03), dolomite (calcium magnesium carbonate, CaCO 3 MgCO 3), and sodium carbonate, Na 2 CO 3.
It may also be accompanied by pyrites, galena, arsenides and antimonides, quartz, calcite, dolomite, &c. It is widely distributed, and is particularly abundant in Germany (the Harz, Silesia), Austro-Hungary, Belgium, the United States and in England (Cumberland, Derbyshire, Cornwall, North Wales).
Here very clean non-magnetic concentrate of willemite, which is an anhydrous zinc silicate and a very highgrade zinc ore, is separated from an intimate mixture of willemite, zincite and franklinites, with calcite and some manganese silicates.
It is often associated with blende and pyrites, and with calcite, fluorspar, quartz, barytes, chalybite and pearlspar as gangue minerals; in the upper oxidized parts of the deposits, cerussite and anglesite occur as alteration products.
calcite reaching from the periphery nearly or quite to the centre of the coral-cup or calicle.
They are principally finely divided quartz, epidote, zoisite, rutile, limonite, calcite, pyrites,.
It is a constituent of the minerals cerussite, malachite, azurite, spathic iron ore, calamine, strontianite, witherite, calcite aragonite, limestone, &c. It may be prepared by burning carbon in excess of air or oxygen, by the direct decomposition of many carbonates by heat, and by the decomposition of carbonates with mineral acids, M2C03+2HC1=2MCl-FH 2 O+CO 2.
gypsum, celestine, aragonite and calcite.
Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc, blende, barytes, calcite and fluor-spar are common.
In the neighbourhood of Nottingham, and other places in the Midlands, barytes forms a cementing material in the Triassic sandstones; amber-coloured crystals of the same mineral are found in the fuller's earth at Nutfield in Surrey; and the septarian nodules in London Clay contain crystals of barytes as well as of calcite.
are included sulphur and ammonium nitrate; monotropy is exhibited by aragonite and calcite.
There are perfect cleavages parallel to the rhombohedral faces, and the crystals exhibit a strong negative double refraction, like calcite.
The divisional planes often contain small films of other minerals, the commonest being calcite, gypsum and iron pyrites, but in some cases zeolitic minerals and galena have been observed.
At Moriah and Port Henry, in Essex county, is a stone known as ophlite marble, a mixture of serpentine, dolomite and calcite interspersed with small flecks of phlogopite.
Calcium carbonate, CaCO 3, is of exceptionally wide distribution in both the mineral and animal kingdoms. It constitutes the bulk of the chalk deposits and limestone rocks; it forms over one-half of the mineral dolomite and the rock magnesium limestone; it occurs also as the dimorphous minerals aragonite (q.v.) and calcite (q.v.).
In the animal kingdom it occurs as both calcite and aragonite in the tests of the foraminifera, echinoderms, brachiopoda, and mollusca; also in the skeletons of sponges and corals.
Hot or dilute cold solutions deposit minute orthorhombic crystals of aragonite, cold saturated or moderately strong solutions, hexagonal (rhombohedral) crystals of calcite.
Aragonite is the least stable form; crystals have been found altered to calcite.
Other minerals which occur in the rocks of this group are calcite, garnet, biotite, chloritoid, epidote, tourmaline and graphite or dark carbonaceous materials.
It also enters (as carbonates) into the composition of many minerals, such as chalk, dolomite, calcite, witherite, calamine and spathic iron ore.
The copper is also accompanied by epidote, calcite, prehnite, analcite and other zeolitic minerals.
Fluor-spar has a hardness of 4, so that it is scratched by a knife, though not so readily as calcite.
The basal plane, so common on calcite and many other rhombohedral minerals, is of the greatest rarity in quartz, and when present only appears as a small rough face formed by the corrosion of the crystal.
Jacob's Cavern (q.v.), near Pineville, McDonald county, disclosed on exploration skeletons of men and animals, rude implements, &c. Crystal Cave, near Joplin, Jasper county, has its entire surface lined with calcite crystals and scalenohedron formations, from I ft.
The walls of the calices and coenenchymal tubes are formed of flat plates of calcite, which are so disposed that the walls of one tube enter into the composition of the walls of adjacent tubes, and the walls of the calices are formed by the walls of adjacent coenenchymal tubes.
The trabeculae are united together by these thickened internodes, and the result is a fenestrated septum, which in older septa may become solid and aporose by continual deposit of calcite in the fenestrae.
in diameter), with often felspar, tourmaline, zircon, epidote, rutile and more or less calcite.
ammonite preserved in a pale yellow calcite.
The photo below shows a fairly large ammonite preserved in a pale yellow calcite.
awkward calcite squeeze near the entrance.
The mineral is regularly found associated with massive barite or calcite.
barite crystals 22 mm long on drusy calcite.
From here a tiny slot through a calcite blockage looked down into darkness.
The sandstones have more quartz and glauconite, and are only loosely cemented together by calcite.
It is harder, denser, and often contains calcite.
Water filtering down through the rock has deposited calcite, gypsum, baryte and celestine in the cracks, sometimes as well-formed crystals.
A SEM image of one ash sample (TES 54) shows platy calcite aggregating as lumps (Fig.
Many questions remain and new ones have arisen: In how many different ways has calcite be used in the construction of visual systems?
The best bit being the river of white calcite encountered close to the end.
Pete climbed up and put his head through the gap and reported a wall of pure white calcite.
In some cases a brown marl is also present, coating the ferroan calcite or directly in contact with the bivalve shell.
The dating of stalagmitic calcite therefore provides a valuable method for understanding cave chronologies.
Bivalve: a group of mollusks with flattened bodies enclosed by a pair shells (valves) made of hard calcite.
more calcite than you can shake a very big stick at.
calcite blockage looked down into darkness.
calcite crystals from quartz crystals by their shape.
calcite cement in thin section, Pwll y Cwm Oolite, Lower Carboniferous, Baltic Quarry, South Wales.
calcite marbles have high Sr contents, averaging 2000 ppm.
calcite formations were seen.
The lime mud is made of the mineral calcite.
At the laboratory scale, experiments are being undertaken to identify the controls upon sulfate incorporation into speleothem calcite.
In geology, the cement of breccias and conglomerates is usually silica, iron oxides or calcite (mineral calcium carbonate ).
Cathodoluminescence micrograph of zoned calcite cement in thin section, Pwll y Cwm Oolite, Lower Carboniferous, Baltic Quarry, South Wales.
In the Bay Complex narrow zones of bleached rock are rich in calcite, chlorite and pyrite and contain minor chalcopyrite and pyrrhotite.
We have used molecular modeling methods to study the interfaces between calcite crystals and monolayers of stearic acid.
This suggests a pure calcite interior with an outer layer of ferroan dolomite.
effervesces slightly in dilute hydrochloric acid thus indicating calcite cement.
Minerals include galena, pyrite, calcite and quartz.
To be perfectly honest, I didn't actually think we would get beyond the awkward calcite squeeze near the entrance.
man-sized hole had been knocked through the calcite barrier - cave preservationists forgive us!
Being regularly washed by wave action at every high tide, the softer marl is soon eroded away from the harder calcite fossils.
These clays contain round nodules of limestone with ammonites preserved in green calcite crystal tho there are very difficult to clean.
platy golden brown barite crystals 22 mm long on drusy calcite.
Dark, zoned calcite of domain 4b is intimately associated with dolomite rhombs.
rhombic crystals on a crust of tiny calcite crystals covering basalt matrix.
rift passage leads off for 60m with calcite flowers on the floor.
sparry calcite preserving the level.
We propose that the crucial mineral added to the murky brown syrup to help produce the crystalline sugar was fine-grained calcite.
An example of such a system is the nucleation of calcite crystals on carboxylic acid terminated alkyl thiols, which produces highly oriented crystals.
Fissures, filled with calcite and sand, were pointed out, thought to be due to brittle fracture, as tectonic uplift occurred.
The water-worn dog-tooth calcite (about 6 " long) at one end presumably indicates development along a calcite vein.
Calcium carbonate separates as hexagonal calcite from cold solutions (below 30Ã‚°), and as rhombic aragonite from solutions at higher temperatures; lead and strontium carbonates, however, induce the separation of aragonite at lower temperatures.
Calcite crystals, drusy, feathery or fern-like, line the sides and bottom of every water-filled cavity, and indeed constitute the sub stance of which they are made.
Rhombic crystals on a crust of tiny calcite crystals covering basalt matrix.
At the cascades, a high rift passage leads off for 60m with calcite flowers on the floor.
Although composed of a single crystal of calcite, a sea urchin plate exhibits a bicontinuous morphology with pores of diameter 10-15 micron.
The remainder of the void then fills with sparry calcite preserving the level.
The water-worn dog-tooth calcite (about 6 long) at one end presumably indicates development along a calcite vein.
Veins of white calcite visible in the stone are considered undesirable, however a dusting of gold pyrite is fine.
Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc blende, barytes, calcite and fluor-spar are common.
Calcium carbonate separates as hexagonal calcite from cold solutions (below 30°), and as rhombic aragonite from solutions at higher temperatures; lead and strontium carbonates, however, induce the separation of aragonite at lower temperatures.
These often have the form of prisms of calcite surrounded by a cuti cular meshwork; the whole is nourished and kept alive by processes, which in Crania are branched; these perforate the shell and permit the access of the coelomic fluid throughout its substance.
Besides the ordinary shell money, there is a sort of stone coinage, consisting of huge calcite or limestone discs or wheels from 6 in.
Second in importance is the carbonate, calamine (q.v.) or zinc spar, which at one time was the principal ore; it almost invariably contains the carbonates of cadmium, iron, manganese, magnesium and calcium, and may be contaminated with clay, oxides of iron, galena and calcite; "white calamine" owes its colour to much clay; "red calamine" to admixed iron and manganese oxides.
Thus the sulphate constitutes the minerals anhydrite, alabaster, gypsum, and selenite; the carbonate occurs dissolved in most natural waters and as the minerals chalk, marble, calcite, aragonite; also in the double carbonates such as dolomite, bromlite, barytocalcite; the fluoride as fluorspar; the fluophosphate constitutes the mineral apatite; while all the more important mineral silicates contain a proportion of this element.
Now, whether a real, though undetected, change occurs is a question to be determined from case to case; it is certain, however, that a substance like aragonite (a mineral form of calcium carbonate) has sensibly persisted in geological periods, though the polymorphous calcite is the more stable form.
The other minerals found in the concentrates are pebbles and fragments of pyrope, zircon, cyanite, chrome-diopside, enstatite, a green pyroxene, mica, ilmenite, magnetite, chromite, hornblende, olivine, barytes, calcite and pyrites.
Pseudomorphs after calcite are known; and it is notable that native copper occurs pseudomorphous after aragonite at Corocoro, in Bolivia, where the copper is disseminated through sandstone.
In some corals the septa are solid imperforate plates of calcite, and their peripheral ends are either firmly welded together, or are united by interstitial pieces so as to form imperforate theca.
Silica forms nearly the whole substance of flint; calcite and dolomite may occur in it in small amounts, and analysis has also detected minute quantities of volatile ingredients, organic compounds, &c., to which the dark colour is ascribed by some authorities.
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