A zone or halo of contact metamorphism found in the country rock surrounding an igneous intrusion. Aureole. Basalt rocks are in some cases classified after their titanium (Ti) content in High-Ti and Low-Ti varieties. Classification of Hornfels – The Hornfels classification of mineral composition that can be seperate into one of three general group The need for stability may cause the structure of minerals to rearrange and form new minerals. High-Ti and Low-Ti basalts have been distinguished in the Paraná and Etendeka traps a nd the Emeishan Traps.. Mid-ocean ridge basalt (MORB) is a tholeiitic basalt commonly erupted only at ocean ridges and is characteristically low in incompatible elements These are classified mainly by the minerals present or the chemical composition of the protolith. Hornfels are heated when near a heat source such as … mineral composition. It has a non-foliated metamorphic rock that has no specific composition. Hornfels Formation. a fine-grained metamorphic rock formed by the action of heat on clay rocks. Hornfels. Hornfels, with its alternating bands of dark and light crystals, is a good example of how minerals rearrange themselves during metamorphism. The stones in South Africa are called “ring-stones” due to their ability to ring like a bell after being struck with an object. High and low titanium basalts. Hornfels formation took place millions of years ago. Fine-grained quartz and feldspar are often abundant in phyllite. There are a variety of Hornfels Uses and the Hornfels Reserves are found in many countries around the world. 1. These properties are due to fine grained non aligned crystals. Example - metamorphism of a shale, made up initially of clay minerals and quartz all of clay or silt size. Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. They form through the low-grade metamorphic transformation of clay minerals. It is composed of the minerals calcite and dolomite. The rock produced is often a fine-grained rock that shows no foliation, called a hornfels. Common types of hornsfel include calcite-silicate hornfels, from limestone and biotite hornfels like shales and slates. Hornfels have the ability to resonate when struck. These mineral grains are usually smaller than what can be easily seen with the unaided eye. Phyllite is composed mainly of tiny grains of mica minerals such as muscovite, or sericite. Composition. Hornfels is a fine-grained metamorphic rock formed by the action of heat on clay rocks, known as contact metamorphism. Hornfels is from a German word means hornstone because of its much hardness and texture both resembled to animal horn is a metamorphic rock. Foliated Metamorphic Rocks . Hornfels are also called as Whetstone in England. The rocks in the earth’s crust continuously undergo changes in their composition which leads to formation of other rocks. Composition of Phyllite. Hornfels can be very hard and durable or splintery and easily fractured along their banded layers. ... Hornfels. Felspar-hornblende-pyroxene hornfels are … Ions may move between minerals to create minerals of different chemical composition. Hornfels is shown in table 1. Name: Hornfels: Texture: Non-foliated; Very fine-grained: Composition: variable: Index Minerals: Color: mottled brownish green: Miscellaneous: Very hard: Metamorphic Type