Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 3 as "calcite". Other polymorphs of calcium carbonate are the minerals vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, vaterite is less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime, calx with the suffix -ite used to name minerals, it is thus etymologically related to chalk. When applied by archaeologists and stone trade professionals, the term alabaster is used not just as in geology and mineralogy, where it is reserved for a variety of gypsum. In publications, two different sets of Miller indices are used to describe directions in calcite crystals - the hexagonal system with three indices h, k, l and the rhombohedral system with four indices h, k, l, i. To add to the complications, there are two definitions of unit cell for calcite.

One, an older "morphological" unit cell, was inferred by measuring angles between faces of crystals and looking for the smallest numbers that fit. A "structural" unit cell was determined using X-ray crystallography; the morphological unit cell has approximate dimensions a = 10 Å and c = 8.5 Å, while for the structural unit cell they are a = 5 Å and c = 17 Å. For the same orientation, c must be multiplied by 4 to convert from morphological to structural units; as an example, the cleavage is given as "perfect on " in morphological coordinates and "perfect on " in structural units. Twinning and crystal forms are always given in morphological units. Over 800 forms of calcite crystals have been identified. Most common are scalenohedra, with faces in the hexagonal directions or directions. Habits include acute to tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms, it may occur as fibrous, lamellar, or compact. A fibrous, efflorescent form is known as lublinite.

Cleavage is in three directions parallel to the rhombohedron form. Its fracture is difficult to obtain. Scalenohedral faces are chiral and come in pairs with mirror-image symmetry. Rhombohedral faces are achiral, it has a defining Mohs hardness of 3, a specific gravity of 2.71, its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, orange, green, violet, brown, or black can occur when the mineral is charged with impurities. Calcite is transparent to opaque and may show phosphorescence or fluorescence. A transparent variety called. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar" while the rhombohedral form is sometimes referred to as "nailhead spar". Single calcite crystals display; this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669. At a wavelength of ≈590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively.

Between 190 and 1700 nm, the ordinary refractive index varies between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, dissolved ion concentrations. Although calcite is insoluble in cold water, acidity can cause dissolution of calcite and release of carbon dioxide gas. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. When conditions are right for dissolution, the removal of calcite can increase the porosity and permeability of the rock, if it continues for a long period of time may result in the formation of caves.

On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, resulting in various forms of karst topography. Ancient Egyptians carved many items out of calcite, relating it to their goddess Bast, whose name contributed to the term alabaster because of the close association. Many other cultures have used the material for similar carved applications. High-grade optical calcite was used in World War II for gun sights in bomb sights and anti-aircraft weaponry. Experiments have been conducted to use calcite for a cloak of invisibility. Microbiologically precipitated calcite has a wide range of applications, such as soil remediation, soil stabilization and concrete repair. Calcite, obtained from an 80 kg sample of Carrara marble, is used as the IAEA-603 isotopic standard in mass spectrometry for the calibration of δ18O and δ13C. Calcite is a common constituent

All Star was an imprint of ongoing American comic book titles published by DC Comics that ran from 2005 to 2008. DC has published two titles under the All-Star banner, featuring Superman; the premise of the imprint was to partner DC Comics' top tier characters with the most popular and acclaimed writers and artists. The creators had access to all elements in the characters' histories to present their interpretation for a modern audience that have not read these DC characters' comics or had not seen them lately; the creative teams were not beholden to any previous and present continuities, told stories that featured "the most iconic versions of these characters". The project had been compared to the Ultimate line of Marvel Comics, a successful attempt to re-introduce Marvel's most popular characters to a new generation of readers by presenting new, updated versions unburdened by decades of plotlines. There were several differences between the two imprints, though. While the Ultimate titles have interrelated storylines, of the two All-Star series released, there has been no effort to make them conform to each other or indicate they exist in the same continuity.

Another is that All-Star did not seek to introduce brand new versions of the characters so much as to present them in unhindered continuity. Robin's origin was the only one "rebooted" in this imprint; some observers, DC themselves, had pointed to the return of DC's major film franchises as an impetus for All-Star. "No one can doubt that some kind of continuity shedding is necessary with Superman and Batman coming to the big screens," the website Comicon.com wrote. "Moviegoers entertained by these films would find the current comics storylines impenetrable ". With the end of Grant Morrison and Frank Quitely's All-Star Superman and the rebranding of Frank Miller and Jim Lee's All Star Batman and Robin as Dark Knight: Boy Wonder as well as the introduction of the DC: Earth One line of OGNs, the imprint is defunct. Only three All-Star titles have been released, although the last title is technically not a part of All Star imprint since it went defunct 2008; the original intent was for the creators to present versions of the DC characters the public could identify with but has since evolved with the creators' sensibilities and story direction.

In that regard, DC Comics has decided that each of the series would end when the creators decide they are done rather than continue with a new creative team. The All-Star titles are self-contained, despite sharing a label; each story within each book has the option of having its own continuity, without ties to previous stories. All Star Batman & Robin, the Boy Wonder is the first title to come out of the All-Star imprint, it premiered on September 2005. The first story arc featured writer Frank Miller; this series features stories set in the early stages of the career of Batman, beginning with his recruitment of Dick Grayson as his sidekick Robin. Vicki Vale, Black Canary, Wonder Woman, Green Lantern, Plastic Man, Batgirl appear. After the series being on hiatus for nearly two years, DC Comics announced on April 2, 2010, that Miller and Lee would return to the series in February 2011. Instead of falling under the "All-Star" print, the series will be re-branded as "Dark Knight: Boy Wonder," and will run for six issues, completing the story Miller intended to tell.

All-Star Batman & Robin the Boy Wonder is in a spin-off continuity set in Frank Miller's "Dark Knight Universe" which consists of Batman: Year One, Spawn/Batman, The Dark Knight Returns, The Dark Knight Strikes Again, The Dark Knight III: The Master Race. As of January 2019 "Dark Knight: Boy Wonder" has not been solicited. All-Star Superman premiered on November 2005; the creative team of writer Grant Morrison and artist Frank Quitely finished their twelve-issue run in 2008. There were discussions with Morrison on a spin-off limited series or special featuring the Super-Sons and Men of Tomorrow, but these plans were canceled. All-Star Batman was an ongoing series that premiered on August 2016 as part of the DC Rebirth relaunch, ran for 14 issues until October 2017; the creative team consisted of writer Scott Snyder and multiple artists John Romita Jr.. Despite the title, the series told stories. There were several other titles announced that would have added to the All-Star lineup but never saw publication.

All Star Wonder Woman was confirmed at the San Diego Comic Con 2006, with Adam Hughes announced as writer and artist. Hughes intended to retell the character's origin story, described his approach to the series as an "iconic interpretation" of the character, but explained at the 2010 San Diego Comic-Con International that the project was "in the freezer" for the time being, due to the difficulty involved in both writing and illustrating himself. All Star Batgirl was announced at the Toronto Comic Book Expo in 2006. Geoff Johns and J. G. Jones were planning to work on the first six issues, which would present a connection between Barbara Gordon and Arkham Asylum. According to Johns, the series would feature "a mystery centering around Barbara Gordon’s transformation into Batgirl," as in Batman: The Long Halloween; the title was described as not taking place in the continuity of All Star Batman and Robin the Boy Wonder. All Star Green Lantern was planned, with the creative team of Cliff Chiang.

It would have starred the John Stewart version of the character. All-Star Superman, a film in the DC Universe Animated Original Movies series, is an adaptation of Grant Morrison and Frank Quitely's 2005–2008 comic book All-Star Superman, it was directed by Sam Liu. It was released on Fe

Matthew Joseph Cohen is an American film and television actor best known for playing young John Winchester and the archangel Michael in Supernatural, Aiden Dennison on the teen drama series South of Nowhere, as Griffin Munro on the ABC daytime soap General Hospital. Cohen was born in Florida, he is Jewish. Cohen ran track in high school, he attended American Heritage School from 2nd to 12th grade and graduated in 2001. Cohen motocross, he graduated with honors. Cohen went to Florida State. While in college, he enrolled in acting classes. After finishing college, Cohen moved to Los Angeles to pursue acting. Cohen has starred in several films such as Boogeyman 2, Dark House and he played lead character Aiden Dennison on The N's South of Nowhere, he played Syd on Rockville CA, a WB web series created by The O. C's Josh Schwartz. In 2009, he co-produced The Outside, which starred Nia Peeples, Michael Graziadei, Dante Basco and South of Nowhere's Rob Moran. In late 2008, he had a guest-starring role in the third episode of The CW's fourth season of Supernatural as a young John Winchester, which he reprised in the fifth-season episode "The Song Remains the Same".

He reappeared in the eleventh season's "Baby," but was revealed to be an unknown being posing as John Winchester to communicate with Sam in his dreams. This being was identified as Lucifer, he portrayed Johnny Jones in the slasher–thriller film Chain Letter. He guest-starred in the fourth season of 90210 after replacing Drew Seeley in the role, it was announced on August 11, 2015, that Cohen was to recur in the second season of How to Get Away with Murder as Levi, described as a sexy, working-class guy. He will appear in a total of three episodes. In 2016, he joined the cast of General Hospital as Griffin Munro. In March 2019, it was announced that Cohen would leave General Hospital, making his last appearance on March 22, 2019. In December 2019, it was announced that Cohen would return to General Hospital for a short period of time. Cohen married his South of Nowhere co-star Mandy Musgrave on May 18, 2011. Mandy gave birth to their son, Macklin, in April 2015. Matt Cohen on IMDb Matt Cohen on Instagram Matt Cohen on Twitter