Cristobalite
Cristobalite spheres formed via devitrification (loss of silica) from the obsidian matrix (California, USA) 5.9×3.8×3.8 cm.
General
Category	Silicate mineral
Chemical formula	SiO2
Strunz classification	4.DA.15
Dana classification	75.1.1.1
Crystal symmetry	Tetragonal (α) space group P41212, cubic (β) Fd3m
Unit cell	a = 4.9709(1) A, c = 6.9278(2) A, Z = 4 (α); a = 7.166 A, Z = 8 (β)
Identification
Color	Colorless, white
Crystal habit	Octahedra or spherulites up to several cm large
Twinning	on {111}
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	6–7
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Specific gravity	2.32–2.36
Optical properties	Uniaxial (-)
Refractive index	nω = 1.487 nε = 1.484
Birefringence	0.003
Pleochroism	None
Melting point	1713 °C (β)[1]
References	[2][3][4]

The mineral cristobalite is a high-temperature polymorph of silica, meaning that it has the same chemical formula, SiO₂, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group which also include coesite, tridymite and stishovite. Cristobalite occurs as white octahedra or spherullites in acidic volcanic rocks and in converted diatomaceous deposits in the Monterey Formation of the US state of California and similar areas. Cristobalite is stable only above 1470 °C, but can crystallize and persist metastably at lower temperatures.

The persistence of cristobalite outside of its thermodynamic stability range occurs because the transition from cristobalite to quartz or tridymite is "reconstructive", requiring the breaking up and reforming of the silica framework. These frameworks are composed of SiO₄ tetrahedra in which every oxygen atom is shared with a neighbouring tetrahedron, so that the chemical formula of silica is SiO₂. The breaking of these bonds required to convert cristobalite to tridymite and quartz requires considerable activation energy and may not happen on a human time frame. Framework silicates are also known as tectosilicates.

There is more than one form of the cristobalite framework. At high temperatures, the structure is cubic, Fd3m, No.227, Pearson symbol cF104.^[5] A tetragonal form of cristobalite (P4₁2₁2, No. 92, Pearson symbol tP12^[6]) occurs on cooling below ca. 250 °C at ambient pressure, and is related to the cubic form by a static tilting of the silica tetrahedra in the framework. This transition is variously called the low-high or Failed to parse (Missing texvc executable; please see math/README to configure.): \alpha-\beta

transition. It may be termed "displacive"; i.e., it is not generally possible to prevent the cubic β-form from becoming tetragonal by rapid cooling. Under rare circumstances the cubic form may be preserved if the crystal grain is pinned in a matrix that does not allow for the considerable spontaneous strain that is involved in the transition, which causes a change in shape of the crystal. This transition is highly discontinuous. The exact transition temperature depends on the crystallinity of the cristobalite sample, which itself depends on factors such as how long it has been annealed at a particular temperature.

The cubic β-phase consists of dynamically disordered silica tetrahedra. The tetrahedra remain fairly regular and are displaced from their ideal static orientations due to the action of a class of low-frequency phonons called rigid unit modes. It is the "freezing" of one of these rigid unit modes that is the soft mode for the α–β transition.

In the α–β phase transition only one of the three degenerate cubic crystallographic axes retains a fourfold rotational axis in the tetragonal form. The choice of axis is arbitrary, so that various twins can form within the same grain. These different twin orientations coupled with the discontinuous nature of the transition can cause considerable mechanical damage to materials in which cristobalite is present and that pass repeatedly through the transition temperature, such as refractory bricks.

When devitrifying silica, cristobalite is usually the first phase to form, even when well outside of its thermodynamic stability range. The dynamically disordered nature of the β-phase is partly responsible for the low enthalpy of fusion of silica.

The micrometre-scale spheres that make up precious opal are made of cristobalite, crystallized metastably at low temperature.

• 

  An idealized model of β-cristobalite, showing corner-bonded SiO₄ tetrahedra. In reality the tetrahedra are constantly tumbling.

• 

  β-cristobalite viewed along another direction.

• 

  The crumpled framework of α-cristobalite, related to the β-form by static tilting of the tetrahedra.

• A-cristobalite.png

  Unit cell of α-cristobalite; red spheres are oxygen atoms.

References[link]

Further reading[link]

• American Geological Institute Dictionary of Geological Terms.
• Durham, D.L., "Monterey Formation:Diagenesis. In: Uranium in the Monterey Formation of California". US Geological Survey Bulletin 1581-A, 1987.
• Reviews in Mineralogy and Geochemistry, vol. 29., Silica: behavior, geochemistry and physical applications. Mineralogical Society of America, 1994.
• R.B. Sosman, The Phases of Silica. (Rutgers University Press, 1965)

External links[link]

• International Chemical Safety Card 0809

David Archuleta
Archuleta in the American Idol Experience motorcade at Walt Disney World (February 2009)
Background information
Birth name	David James Archuleta
Born	(1990-12-28) December 28, 1990 (age 21)[1] Miami, Florida
Origin	Murray, Utah, United States
Genres	Pop[2]
Occupations	Singer-songwriter, actor
Instruments	Vocals, piano, keyboards, guitar
Years active	2003–present
Labels	Jive[3] (2008–2011) Ivory Records[4] (2011–present)
Website	www.davidarchuleta.com

David James Archuleta (born December 28, 1990) is an American pop singer-songwriter. At ten years old he won the children's division of the Utah Talent Competition leading to other television singing appearances.^[5] When he was twelve years old, Archuleta became the Junior Vocal Champion on Star Search 2.^[5] In 2007, at sixteen years old, he became one of the youngest contestants on the seventh season of American Idol.^[6] In May 2008 he finished as the runner-up, receiving 44 percent of over 97 million votes.

In August 2008 Archuleta released "Crush," the first single from his self-titled debut album.^[5][7][8][9] The album, released three months later, debuted at number two on the Billboard 200 chart; it has sold over 750,000 copies in the U.S., and over 900,000 worldwide.^[10][11][12] In October 2010 he released a third album, The Other Side of Down featuring lead single "Something 'Bout Love". In 2011, Archuleta announced he is taking a two-year hiatus to be a missionary of The Church of Jesus Christ of Latter-day Saints.^[13][14] As of February 2012, Archuleta has sold 1,108,000 albums and 3,327,000 tracks in the United States.^[15]

Early life[link]

Archuleta was born in Miami, Florida, to Jeff Archuleta and Lupe Marie Mayorga. His mother is a salsa singer and dancer from Honduras and his father is a jazz musician of Spanish-Basque descent;^[16] he speaks a little bit of Spanish and aspires to learn more.^[17] Archuleta has four siblings.^[18] His family moved to the Sandy, Utah, suburb of Salt Lake City when he was six. He now lives in Murray where he attended Murray High School.^[19] He is a former Boy Scout and is a member of The Church of Jesus Christ of Latter-day Saints.^[20]

Archuleta started singing at the age of six, inspired by a Les Misérables video. "That musical is what started all of this", he said.^[21] He started performing publicly at age ten when he participated in the Utah Talent Competition, singing "I Will Always Love You" by Dolly Parton; he received a standing ovation and won the Child Division.^[22]

Music career[link]

2003–06: Star Search and musical beginnings[link]

In 2003, when he was twelve years old, Archuleta sang on several episodes of the television show Star Search.^[23][24][25] He ended up as the Junior Vocal Champion on Star Search 2, Losing the Junior Grand Champion title to Tiffany Evans.^[26] On one episode, he sang against then-11-year-old Alexandréa Lushington, who became a "top 20" semi-finalist on American Idol alongside Archuleta.^[24] Around the second year of being on Star Search he started focusing on the lyrics, "I didn't even pay attention to the lyrics when I was 12, 13".^[27]

Archuleta's competing on Star Search was preceded by an appearance on The Jenny Jones Show, meeting the finalists from American Idol's first season, for whom he performed a spontaneous a cappella rendition of "And I Am Telling You I'm Not Going" from Dreamgirls. He received praise from Season 1 winner Kelly Clarkson,^[27][28] and the episode led to appearances on CBS's The Early Show. The year after Star Search, he found out he had partial vocal paralysis but declined risky surgery and has said he feels he is almost fully recovered.^[21][27] He limited his singing for specific occasions like Stadium of Fire, the Independence Day celebration at Brigham Young University Stadium.^[27]

Archuleta made initial attempts at songwriting and arranging music after his star search experience and has written at least three songs.^[27] His first singles in 2002 included "Dream Sky High" and "Don't Tell Me".^[29]

[edit] 2007–08: American Idol and David Archuleta

Archuleta received his ticket to the Hollywood final auditions at the San Diego tryouts – held at Qualcomm Stadium at the end of July 2007 – with a performance of John Mayer's "Waiting on the World to Change" with judge Randy Jackson spontaneously joining in to sing the background "waiting" in the song.^[22][30] He was sixteen during the Hollywood auditions and attended school while a part of American Idol's seventh season.^[6] His parents were there because he was a minor.^[6] Archuleta also took advantage of the decision to allow contestants to play musical instruments when he accompanied himself on piano for his performances of "Crazy", "Another Day in Paradise", and "Angels".

During the 1970s themed week Archuleta sang the John Lennon song "Imagine", omitting the earlier verses in favor of the last one. Los Angeles Times columnist Ann Powers speculated that he wanted to avoid singing "no religion too" because of his faith. "As a Mormon, he's unlikely to espouse the song's agnostic ideal," she wrote.^[31] However, he did sing the entire song on Good Things Utah when he was thirteen. When asked by judge Randy Jackson why he didn't sing the first verse, Archuleta said the third verse was his favorite because it has "a great message."^[32]

After his performance of "We Can Work It Out", which judge Simon Cowell called "a mess", Entertainment Tonight reported that Archuleta was feeling pressure from his father, Jeff Archuleta, who "reportedly yelled at" his son after a recording session the previous night.^[33] Jeff Archuleta, in an interview with Us Weekly, denied the claim.^[34][35] A May 2008 Associated Press article reported that Jeff Archuleta had his son add a lyric from the Sean Kingston song "Beautiful Girls" into an interpretation of "Stand by Me" (from which "Beautiful Girls" samples its bass line), increasing the costs for licensing, and that this had resulted in Jeff Archuleta being banned from American Idol backstage rehearsals.^[36] Archuleta defended his father calling him "a great guy" who keeps him grounded.^[37]

During the Top 7 results show, the contestants were split into two groups. In one group was Syesha Mercado, Brooke White, and Kristy Lee Cook. In the other group was David Cook, Carly Smithson, and Jason Castro. Archuleta was the only one not sorted into a group. He was declared safe after the groups were formed, then was asked to choose the group he thought was safe. He refused, and sat down on the floor of the stage, much like Melinda Doolittle had done the previous season.

In the finale he sang "Don't Let the Sun Go Down on Me", "In This Moment" and "Imagine". Judge Simon Cowell declared that Archuleta won the evening and even David Cook, who ultimately won, thought Archuleta would win: "I have to concede it, the kid came out all three songs and nailed it", said Cook.^[38] In the final tally, Archuleta received 44 percent of the votes.^[39][40] During the finale show, identical commercials featuring Archuleta and fellow finalist Cook mimicked the Tom Cruise scene from Risky Business where he dances in his underwear playing an air guitar; they were promoting the game franchise Guitar Hero.^[41]

Archuleta performing during the American Idols LIVE! Tour 2008

Archuleta's first appearances on music ranking charts were with the three songs he performed in the American Idol finale; "Don't Let the Sun Go Down on Me", "In This Moment", and "Imagine", debuted on the Billboard Hot 100 chart the week of June 7, 2008. "Imagine" entered at number 36 (giving Archuleta his first top forty hit), "Don't Let the Sun Go Down on Me" at number 58, and "In This Moment" entered at number 60.^[43] That same week he had three songs on Billboard's Bubbling Under Hot 100 Singles chart as well, where his versions of "Longer", "Think of Me", and "Angels" debuted at number 15, number 19, and number 24 respectively.^[44] In July 2008 So You Think You Can Dance, a dance competition reality show, Archuleta's cover of "Imagine" by John Lennon was the featured music for contestants Katee Shean and William Wingfield with their pas de deux performance.^[45]

Archuleta signed with Jive Records in June 2008. His self-titled album, David Archuleta, was released in November 2008. His first single "Crush" was released in August 2008 on Z100, a New York radio station.^[7][46] On August 12 "Crush" became available on iTunes.^[47] It debuted at number two on the Billboard Hot 100, beaten only by Rihanna's "Disturbia".^[48] It was the best chart debut in more than 18 months.^[49] According to Nielsen SoundScan, the track sold 166,000 downloads in the first week in the United States.^[50] It has sold 1.92 million digital copies in the US.^[51]

Archuleta signs autographs while serving as Grand Marshal at the Krewe of Caesar Mardi Gras parade in Metairie, Louisiana, on Valentines Day, 2009.

Along with American Idol winner David Cook, Archuleta placed second on Forbes' list of "Breakout Stars of 2008".^[52] The two co-presented an award at the 2008 Teen Choice Awards in August 2008.^[53] Archuleta also received the Teen Choice Award surfboard for "Most Fanatic Fans".^[53]

[edit] 2009–present: Christmas from the Heart, The Other Side of Down, Forevermore and Begin

Since the release of his debut album, Archuleta has released three new songs: "Let's Talk About Love (The Build-A-Bear theme song)," "Save the Day (released only in Japan as a bonus track in his album)," and "Zero Gravity." In February, it was announced that Archuleta will be touring the United Kingdom supporting British band McFly on their "Up Close...And This Time It's Personal" tour.^[54] The tour began on April 21, 2009 and continued until May.^[54] Archuleta became the opening act for Demi Lovato's tour which began June 21, 2009.^[55]

On April 22, 2009, Archuleta returned to the American Idol stage in its eighth season and performed the third single from his debut album, "Touch My Hand".^[56] On April 30, 2009 he made his first UK television appearance, on the Paul O'Grady Show, performing "Crush" and chatting about his album, which was released there in May. In May, Archuleta and fellow American Idol David Cook, visited the Philippines.^[57] Two days later he made live appearances on two of GMA-7's shows, Sis and Eat Bulaga. He also confirmed that month that he was working on two new albums, his sophomore pop album and a Christmas album.^[58] In August 2009, Archuleta won three Teen Choice Awards for Breakout Artist, Love Song, and the Music Tour category with Demi Lovato.^[59] In September he won the Year in Music – Rising Male Star award at the ALMA Awards and performed a cover of the standard "Contigo en la Distancia".

Archuleta's acting debut was when he appeared as himself for his acting debut on Nickelodeon's show iCarly titled "iRocked the Vote". The episode aired February 7, 2009. He had also made a special guest appearance in Season 3 of the Disney Channel show Hannah Montana^[60] In the episode "Promma Mia" as himself and he sang a duet: "I Wanna Know You" with Miley Cyrus who plays the title character; the song was featured on the soundtrack, Hannah Montana 3.

On May 16, 2009, Archuleta and David Cook performed in the Mall of Asia: Concert Grounds for their Back-to-Back Concert in Manila, Philippines. On June 1, 2010, Archuleta released Chords of Strength: A Memoir of Soul, Song, and the Power of Perseverance, a memoir which refers to "the partial vocal paralysis he suffered in 2004 but has now fully recovered from". He went on a book signing tour beginning in Ridgewood, New Jersey.^[61] The book was a bestseller.^[62]

Archuleta came back to the American Idol stage on April 7, 2010 on the show's ninth season and performed John Lennon's "Imagine", which David had performed previously in the Top 20 Week when he was a contestant on the show. After his performance, he mentioned that he was working on his third studio album.

Archuleta sang "The Star-Spangled Banner" and "Stand by Me" at the 30th anniversary of the annual A Capitol Fourth concert in Washington, D.C. on the Fourth of July. The show was aired on PBS at 8pm EST live and tape delay PT.^[63]

Archuleta sang live at the Tejano Music Awards covering Selena's songs, Como La Flor and No Me Queda Más at the event as a tribute on July 11, 2010.^[64]

In an interview with AOL's Something Pitchy, Archuleta revealed that the release of his next album is planned for Fall 2010 (he did mention a late September release, but then went back to the Fall). On June 24, 2010 Jive Records announced that his new single would be released on DavidArchuleta.com on July 13, and iTunes on July 20. However, on June 30, 2010 the full version of "Something 'Bout Love" became available to play on his website. His album The Other Side of Down was released on October 5, 2010.^[65]

On October 7, 2010, it was announced that David Archuleta would be the guest star at the annual Christmas concert of the Mormon Tabernacle Choir. Archuleta was scheduled to sing in performances on December 16–19.^[66]

On February 18, 2011 it was announced by Jive Records that David Archuleta had been released from his contract with them. It was also announced on February 17, 2011 that Archuleta left his management Wright Entertainment Group.^[67] Archuleta intends to spend time working on writing original material.^[68]

On July 2, 2011, Archuleta joined Brad Paisley to perform at the Stadium of Fire, where he performed the national anthem in addition to his five song set.^[69] From July 16 to 26, 2011, Archuleta toured Asia, performing in Indonesia, Philippines, Vietnam (Hanoi and Ho Chi Minh), and Malaysia.^[70]

In early 2012, Archuleta signed a contract with TV5 to shoot a primetime mini series in the Philippines titled Nandito Ako (Here I Am), which was broadcast in February and March of 2012.^[71] An Original Pilipino Music album was released in March 26, 2012 in the Philippines, titled Forevermore.^[72] This album contains covers of classic Filipino songs, including "Nandito Ako" (an Ogie Alcasid original), "Forevermore" (a Side A original), and "Rainbow" by South Border. ^[73]

At the conclusion of the December 19, 2011 show of the My Kind of Christmas Tour, Archuleta announced his intention to serve as a missionary for The Church of Jesus Christ of Latter-day Saints for two years. He stated that he would return to music upon the completion of his mission.^[13] Archuleta, who has reportedly been assigned to Chile, entered the Provo, Utah Missionary Training Center on March 28, 2012.^[74]

According to Archuleta's official site, he will release a brand new album titled "Begin", on August 7, 2012 in the United States.^[75] The album will consist of original songs as well as cover songs.

Philanthropy[link]

Along with Do Something and the Dunkin' Brands Community Foundation,^[76] Archuleta is involved with helping willing teenagers make a difference in others' lives with disaster relief.^[77] He is also one of several teen celebrities taking part in DoSomething.org's Teens for Jeans charity initiative, which donates denim to homeless teenagers nationwide.^[78] In January 2010, Haiti was hit with a major earthquake. On January 22, 2010, Archuleta joined other celebrities for a 2-hour fundraising telethon where he answered phones, and even stayed longer afterward to keep answering the phones.^[79]

In January 2011, Archuleta travelled to Chennai, India with Rising Star Outreach,^[80] a non-profit charity giving children from leper colonies a first-class education and a chance at a future in India.^[81]

Archuleta was one of the many Latino singers who participated in Somos El Mundo, the Spanish version of "We Are The World 25 for Haiti".^[82] The song and video premiered on the Cristina Show in March 2010, funds raised benefit Haiti relief.

In support of ChildFund, Archuleta partnered with the charity for his My Kind of Christmas Tour in an effort to increase awareness and recruit new sponsors for children in need worldwide.^[83]

Musical influences[link]

Archuleta's mother is from Honduras, and much of the music he listened to as a child was Latin-influenced, including watching his mom sing at events with her sisters.^[27][84] She also "was big on dancing" according to Archuleta, and would "make" him dance to traditional music with his older sister.^[85] He also listened to jazz music, he said, from his father's collection as well as gospel, pop, rock and "soulful music."^[21] In a later interview, he revealed that his father was a jazz musician. Archuleta also said he enjoys Broadway musicals.^[86]

On his American Idol "Fast Facts" page, Archuleta cited his musical influences as Natalie Cole, Stevie Wonder, Kirk Franklin and Bryan Adams.^[22] Like Elliott Yamin and another singer he admires, John Mayer, Archuleta tries to infuse his pop selections with a soulful vibe.^[21] In a Seventeen interview he cites Sara Bareilles as a clever singer-songwriter whom he looks up to.^[87]

Discography[link]

• David Archuleta (2008)
• Christmas from the Heart (2009)
• The Other Side of Down (2010)
• Forevermore (Philippines release) (2012)
• Begin (2012)^[88]

Filmography[link]

Tours[link]

As main act

• American Idols LIVE! Tour 2008 (2008)
• David Archuleta Live In Concert (2009)
• Christmas from the Heart Tour (2009)
• The Other Side of Down Asian Tour (2011)
• My Kind of Christmas Tour (2011)

As supporting act

• McFly Up Close and This Time It's Personal Tour (2009)
• Demi Lovato Summer Tour 2009 (2009)

Awards and nominations[link]

Notes[link]

References[link]

External links[link]

Wikimedia Commons has media related to: David Archuleta

• Official website
• David Archuleta at the Internet Movie Database
• David Archuleta at YouTube
• Video and audio clips from Archuleta's official website prior to 2006.
• David Archuleta at American Idol