This vibrant, colorful necklace is strung with beads of jasper, garnet, agate, and
calcite on a length of braided cord.
Created using cultured freshwater pearl and turquoise - hued
calcite on a polyester waxed cord, this multi-gem necklace is simple and elegant.
Not exact matches
Unlike typical crystal structures like shells, which incorporate thousands of smaller, geometrically symmetrical crystals attached to each other, each spine
on a sea urchin is a single large
calcite crystal with its own convoluted shape.
They suspect that vaterite may be present
on more plant species, but that the unstable mineral is being converted to
calcite when exposed to wind and rain.
The thin
calcite deposits
on cave art can be contaminated by new flows of uranium - containing water, dust, or other detritus, making the art seem older than it is, he and his colleagues argued.
This would also explain the unusual lack of typical pond fossils at the site, as well as the near lack of gnaw marks
on bones and
calcite and barite concretions found
on bones excavated from the quarry.
Up to now previous investigations focused
on calcite or aragonite saturation state as indicators of calcifiers thresholds, which may completely miss the vulnerability of many calcifiers.
This guarantees further research into the topic, especially
on the Mg -
calcite solubility to further understand how organisms cope with these seawater conditions.
Williams looked at the radioactive elements uranium and thorium trapped in these
calcite crystals, using them as a kind of clock based
on the rate at which uranium decays into thorium.
This is a scanning electron microscopy image of a
calcite crystal generated in the presence of the sea urchin protein rSpSM50
on a silicon wafer showing organized nanotexturing
on exposed surfaces.
To find out whether acid rain was indeed the problem, the team focused
on one problematic sliding layer in the Jiweishan avalanche: a thin bed of black shale, which contains slippery clay minerals such as talc, in addition to fine organic material and
calcite, which helps cement the shale together.
Multiple forms often nucleated in a single experiment — at least one
calcite crystal formed
on top of an aragonite crystal while vaterite crystals grew nearby.
The
calcite builds up in layers, creating uneven surfaces during growth, like steps and terraces
on a mountainside.
These spheres called micelles are molecules that roll up like roly - poly bugs based
on the chemistry along their bodies — pointing outwards are the parts of their molecules that play well chemically with both the surrounding water and the
calcite, while tucked inside are the parts that don't get along with the watery environment.
In this image, researchers observe distortions in the reaction front (the boundary between the blue and red regions) as they form
on the surface of the
calcite mineral, driven by the high solution acidity where the reaction fronts become unstable.
Handcrafted of quartz and
calcite, it blooms
on a circlet of glittering glass crystal.
Carnelian, jasper and quartz mingle with agate,
calcite, amazonite and garnet
on a graceful spiral.
They eat away at him while at the same time building up, like
calcite, weighing
on him, toughening him.
The salt that forms
on the surface of concrete (efflorescence) is often a combination of calcium sulphate (gypsum), salt (sodium chloride) and calcium carbonate (
calcite).
Go
on a guided tour to see the stalactites and stalagmites of Fairy Cave and the
calcite - rimmed pools of Royal Cave.
Rain falling
on this material dissolved some of the
calcite skeletal fragments and then precipitated this
calcite in between other grains to cement all of the grains together and turn the material into a limestone.
The color yellow persists as paint residue
on the excavator heads and is reflected again in the yellow - hued banded
calcite, which, though mined by similar machinery through a process of destruction, now rests in perfect equilibrium in the grip of the sculpture — an essential part of the work.
The afternoon sessions
on water isotopes in precipitation was quite exciting because of the number of people looking at innovative proxy archives, including cave records of 18O in
calcite, or deuterium in leaf waxes, which are extending the coverage (in time and space) of this variable.
The Patagonian Shelf Break lies
on the northern edge of a region that some scientists refer to as the «great southern coccolithophore belt» or the «great
calcite belt.»
On the Gakkel Ridge,
calcite preservation is excellent and Holocene strata are consistently documented to be at least 4 to 20 cm thick.
Similarly, dissolved CO2 in the oceans can precipitate to form
calcite, which is then deposited
on the plate and likewise recycled into the mantle.»
Now let's look at Keigwin's justly famous Sargasso Sea dO18 proxy temperature reconstruction: (1996) «The Little Ice Age and Medieval Warm Period in the Sargasso Sea» Science 274, 1503 - 1508 This isn't meant as a general criticism, however, the reconstructed Sargasso Sea paleotemperature rests
on Globigerinoides ruber
calcite.
This shows the effect of historically invisible confounding influences
on T: dO18 proxy reconstructions, and explicitly refutes your claim, Kau, that, «ONLY a change in temperature or a change in seawater δ18O can alter the δ18O ratio of foraminiferal
calcite.
At some times of year, acidification has already reached a critical threshold for organisms living
on Alaska's continental shelves.145 Certain algae and animals that form shells (such as clams, oysters, and crab) use carbonate minerals (aragonite and
calcite) that dissolve below that threshold.
Past hypotheses arguing calcification was dependent
on carbonate ion concentration, or aragonite and
calcite saturation levels, were most likely misled by the fact that higher carbonate ion concentrations are a daily «side effect» of photosynthesis.
By ruling out the unsuitable elements
on the periodic table and then through modeling of stratospheric chemistry, the team landed
on calcite, a constituent of rocks like limestone, marble and chalk, and one of the Earth's crust's most common compounds.
But since corals, be it with an aragonite or a
calcite skeleton, both rely
on symbiotic algae as their main source of energy they remain vulnerable, since those algae are highly susceptible to both low pH and high temperatures.
I wonder if the described mechanism — CO2 making a hydrogen bond at a surface, then flipping along a fracture plane penetrating deeper into a crystalline material — also works
on calcite and aragonite?
The magnitude of sea - level estimates for the past 100 million years rely heavily
on foraminiferal
calcite oxygen isotopes (δ18O), which are influenced by temperature, evaporation and precipitation, and diagenesis2.