化學組成, 鍵及結構：角鐵的結構非常有特色。很少有任何礦物顯示出結晶形式，但是小顆粒像馬賽克的碎片一樣緊密地結合在一起; 它們通常具有幾乎相同的尺寸。這被稱為pflaster或路面結構從粗糙的路面工作的相似之處。每種礦物質也可以包圍其他顆粒; 在石英中，例如石墨，黑雲母，氧化鐵，矽線石或長石的小晶體可能出現很多。通常這些穀物都是以這種方式呈現半透明的。最小的晶體可能顯示出結晶輪廓的痕跡; 無疑它們具有新的形成，並且始於原地。這導致我們相信整個岩石已經在高溫和固態下重結晶，因此礦物分子幾乎沒有自由來建立良好個性化的晶體。岩石的再生已足以消除大部分原始結構，並且或多或少地完全用新礦物代替原礦物。

它的化學組成是Fe-O-MgO-Al2O3-SiO2-H2O。

Chemical composition, bonding and structure:

The structure of the hornfels is very characteristic. Very rarely do any of the minerals show crystalline form, but the small grains fit closely together like the fragments of a mosaic; they are usually of nearly equal dimensions. This has been called pflaster or pavement structure from the resemblance to rough pavement work. Each mineral may also enclose particles of the others; in the quartz, for example, small crystals of graphite, biotite, iron oxides, sillimanite or feldspar may appear in great numbers. Often the whole of the grains are rendered semi-opaque in this way. The minutest crystals may show traces of crystalline outlines; undoubtedly they are of new formation and have originated in situ. This leads us to believe that the whole rock has been recrystallized at a high temperature and in the solid state so that there was little freedom for the mineral molecules to build up well-individualized crystals. It’s composition is Fe-O-MgO-Al2O3-SiO2-H2O.

原生物：(化石)

Hornfels is a metamorphic rock formed by the contact between mudstone / shale, or other clay-rich rock, and a hot igneous body, and represents a heat-altered equivalent of the original rock. This process is termed contact metamorphism. Because pressure is not a factor in the formation of hornfels, it lacks the foliation seen in many metamorphic rocks formed under high pressure and temperature regimes. Pre-existing bedding and structure of the parent rock is generally destroyed during the formation of hornfels.

Living Specimens: (Fossil)

紋理 – 顆粒狀，片狀或細長晶體隨機取向，因此無明顯的葉理。

粒度 – 非常細膩; 晶體需要在顯微鏡下觀察; 可以包含圓形的 斑晶體。

硬度 – 硬（通常顯示 貝殼狀斷口）。

顏色 – 可變，通常是灰色到黑色，但可以根據母岩成分的不同形成各種顏色。

Texture – granular, platy or elongate crystals randomly oriented so no foliation evident.

Grain size – very fine grained; grains need to be observed under a microscope; can contain rounded porphyroblasts.

Hardness – hard (commonly displays conchoidal fracture).

Colour – variable, generally grey to black, but can form in a variety of colours dependent on parent rock composition.

localised occurrences associated with igneous rocks, e.g. Whangarei Heads, Tokatoka (Kaipara area), Paritu (northern Coromandel Peninsula), west Nelson area.

邁克爾泰林格在南非描述這些石頭，因為它們像響鈴一樣響起，也被稱為“環形石頭”。

Michael Tellinger had described these stones in South Africa also known as “ring-stones” due to their ability to ring like a bell.