方解石柱状晶体（Columnarcalcite）
产地：广西桂林
特征：
方解石是一种碳酸钙矿物，天然碳酸钙中最常见的就是它。因此，方解石是一种分布很广的矿物。方解石的晶体形状多种多样，它们的集合体可以是一簇簇的晶体，也可以是粒状、块状、纤维状、钟乳状、土状等等。敲击方解石可以得到很多方形碎块，故名方解石。硬度分类中标准矿物之一。
方解石经常可以见到良好的晶体，常见晶形有六方柱{1010}和菱面体{0112}的聚形、复三方偏三角面{2131}、菱面体{0112}等，菱面体{1011}单形晶体（与解理块状形状一样）比较少见；依（0112）成聚片双晶者常见，系受应力作用的结果；也呈{0001}接触双晶。集合体呈粒状、致密块状、钟乳状、结核状、鲕状、豆状、土状（白垩）等。
具有{0001}和{1011}形态的方解石是热液早期的产物，形成温度在250～350℃以上；{1010} + {0112}聚形方解石形成温度范围为250～150℃；尖菱面体方解石形成温度为75～25℃(李荣清，1994)。一般认为六方柱晶形出现在较低温的结晶环境(潘兆橹等，1994)。Columnarcalcite
Provenance: Guilin, Guangxi, China
Characteristics:
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380–470 °C, and vaterite is even less stable.
Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals. However, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain.
It has a defining Mohs hardness of 3, a specific gravity of 2.71, and its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities.