大理石
大理石是一種變質岩，形成於石灰岩在變質作用的熱壓環境下。當其源自雜質極少的石灰岩時，會呈現白色。主要成分為礦物方解石（CaCO₃），通常還含有黏土礦物、雲母、石英、黃鐵礦、氧化鐵及石墨等其他礦物。在變質作用條件下，石灰岩中的方解石重新結晶，形成由相互交錯的方解石晶體構成的岩石。當白雲岩承受熱壓作用時，則會產生相關岩石——白雲質大理石。
礦物學：含95%方解石（CaCO₃）或白雲石（Ca,Mg(CO₃)₂）。雜質可能形成新礦物，如橄欖石。
大理石的形成過程
多數大理石形成於匯聚型板塊邊界，該處廣闊地殼區域承受區域性變質作用。部分大理石亦透過接觸變質作用形成，即當高溫岩漿體加熱鄰近石灰岩或白雲岩時產生。
變質作用發生前，石灰岩中的方解石常以岩石化化石材料及生物碎屑形式存在。變質作用期間，這些方解石重新結晶，岩石組織隨之改變。在石灰岩轉化為大理石的初期階段，岩石中的方解石晶體極為微小。於新剖切的手標本中，僅當岩石在光線下晃動時，方能從其細微解理面上瞥見如糖粒般閃爍的光芒。
隨著變質作用深化，晶體逐漸增大，可清晰辨識為相互交錯的方解石晶體。重結晶作用使石灰岩原有的化石與沉積構造模糊化，且此過程不會形成片理——片理通常見於受聚合板塊邊界定向壓力作用而變質的岩石。
再結晶作用是區分石灰岩與大理石的關鍵。經歷低程度變質作用的大理石會形成極細小的方解石晶體，隨著變質程度加深，晶體逐漸增大。當變質作用加劇時，大理石中的黏土礦物會轉變為雲母及更複雜的矽酸鹽結構。
顏色：大理石通常屬淺色岩石。當其源自雜質極少的石灰岩時，呈現純白色澤。若含有黏土礦物、氧化鐵或瀝青質等雜質，則可能呈現藍灰色、粉紅色、黃色或黑色。
極高純度且呈亮白色的大理石用途廣泛。此類石材經開採、粉碎成粉後，會進一步加工以去除盡可能多的雜質，最終產物稱為「白堊粉」。此粉末可用作顏料與填充劑，廣泛應用於油漆、白灰、填縫劑、塑膠、填縫材料、化妝品、紙張及其他工業製品中。
酸性反應：大理石由碳酸鈣構成，接觸多種酸類時會產生反應並中和酸性，是效果最顯著的酸性中和材料之一。常將大理石粉碎後用於溪流、湖泊及土壤的酸性中和處理。
化學工業亦運用大理石進行酸性中和。藥用抗酸劑如「泰諾」含碳酸鈣成分，其原料有時即為大理石粉末。此類藥物有助緩解胃酸逆流或消化不良症狀。大理石粉亦作為惰性填充劑應用於其他藥丸製程。
硬度：大理石主要成分為方解石，莫氏硬度為3級。此特性使其易於雕刻，成為雕塑與裝飾藝術品的理想載體。大理石的半透明特性使其在各類雕塑中尤為引人注目。
大理石的低硬度與可溶性使其能作為動物飼料的鈣質添加劑，對乳牛與蛋雞尤為重要。同時亦可用作低硬度研磨劑，清潔浴室及廚房設備。
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問題
1. 請透過造訪座標位置回答下列問題：
A. 大理石是一種變成岩，形成於石灰岩在變成作用的熱壓作用下。關於gz座標處的大理石有何特徵？由於大理石源自石灰岩，此類岩石中常發現化石。此處可見化石嗎？若有，屬於何種類型？（海百合／珊瑚／腕足動物）
B. 岩石呈現何種色澤（淺色／中色／深色）？其紋理與雜質呈現何種色調？
C. 照片中A、B、C、D哪個字母代表gz座標處的特徵？大理石中的雜質可能形成什成什麼後果？
D. 估計gz座標處中方解石或白雲石所佔百分比為何？
2. 拍攝個人、小組或GPS定位器照片（需在拍攝地點完成），且照片不得透露任何解答內容。
Marble
Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. When it is formed from a limestone with very few impurities, it will be white in color. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite. Under the conditions of metamorphism, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. A related rock, dolomitic marble, is produced when dolostone is subjected to heat and pressure.
Mineralogy: 95% calcite (CaCO3) or dolomite Ca,Mg(CO3)2. Impurities may give rise to new minerals such as olivine.
How marble is formed
Most marble forms at convergent plate boundaries where large areas of Earth's crust are exposed to regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone.
Before metamorphism, the calcite in the limestone is often in the form of lithified fossil material and biological debris. During metamorphism, this calcite recrystallizes and the texture of the rock changes. In the early stages of the limestone-to-marble transformation, the calcite crystals in the rock are very small. In a freshly-broken hand specimen, they might only be recognized as a sugary sparkle of light reflecting from their tiny cleavage faces when the rock is played in the light.
As metamorphism progresses, the crystals grow larger and become easily recognizable as interlocking crystals of calcite. Recrystallization obscures the original fossils and sedimentary structures of the limestone. It also occurs without forming foliation, which normally is found in rocks that are altered by the directed pressure of a convergent plate boundary.
Recrystallization is what marks the separation between limestone and marble. Marble that has been exposed to low levels of metamorphism will have very small calcite crystals. The crystals become larger as the level of metamorphism progresses. Clay minerals within the marble will alter to micas and more complex silicate structures as the level of metamorphism increases.
Color: Marble is usually a light-colored rock. When it is formed from a limestone with very few impurities, it will be white in color. Marble that contains impurities such as clay minerals, iron oxides, or bituminous material can be bluish, gray, pink, yellow, or black in color.
Marble of extremely high purity with a bright white color is very useful. It is often mined, crushed to a powder, and then processed to remove as many impurities as possible. The resulting product is called "whiting." This powder is used as a coloring agent and filler in paint, whitewash, putty, plastic, grout, cosmetics, paper, and other manufactured products.
Acid Reaction: Being composed of calcium carbonate, marble will react in contact with many acids, neutralizing the acid. It is one of the most effective acid neutralization materials. Marble is often crushed and used for acid neutralization in streams, lakes, and soils.
It is used for acid neutralization in the chemical industry as well. Pharmaceutical antacid medicines such as "Tums" contain calcium carbonate, which is sometimes made from powdered marble. These medicines are helpful to people who suffer from acid reflux or acid indigestion. Powdered marble is used as an inert filler in other pills.
Hardness: Being composed of calcite, marble has a hardness of three on the Mohs hardness scale. As a result, marble is easy to carve, and that makes it useful for producing sculptures and ornamental objects. The translucence of marble makes it especially attractive for many types of sculptures.
The low hardness and solubility of marble allows it to be used as a calcium additive in animal feeds. Calcium additives are especially important for dairy cows and egg-producing chickens. It is also used as a low-hardness abrasive for scrubbing bathroom and kitchen fixtures.
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Questions
1. Answer the questions under by visiting the Coordinates.
A. Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. What can you say about the Marble at gz? And as Marble is formed from limestone, you often find fossils in these types of stones. Can any fossils be seen here? If so, what types of fossils? (crinoids/corals/brachiopods)
B. Why is the stone color (light/medium colored/dark)? And what color are the veins and impurities?
C. What letter from the photo A, B, C or D represent what you have at GZ? And what is it that the impurities in the marble stone may give rise to?
D. How many % of calcite or dolomite would you guess is in this marble stone at gz?
2. Take a photo of you, the group or the GPS from the location without revealing any of the answers.