ultramafic rock
121Mafic — is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words magnesium and ferric .[1] Most mafic minerals are dark in color and the relative density is greater than 3. Common… …
122Olivine — For the river in New Zealand, see Olivine River. Olivine General Category Mineral Group Ch …
123Sill (geology) — In geology, a sill is a tabular pluton that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive… …
124Jasperoid — is a rare, peculiar type of metasomatic alteration and occurs in two main forms; sulfidic jasperoids and hematitic jasperoids. True jasperoids are different from jaspillite, which is a form of metamorphosed chemical sedimentary rock, and from… …
125Troctolite — is a rare ultramafic intrusive rock type. It consists essentially of variable amounts of olivine and calcic plagioclase along with variable minor pyroxene. It thus is midway between peridotite and anorthosite.Troctolite is found in some… …
126Vaalbara — is theorized to be Earth s first supercontinent, beginning its formation about 3,600 million years ago, completing its formation by about 3,100 million years ago and breaking up by 2,500 million years ago. The name Vaalbara is de …
127amphibole — /am feuh bohl /, n. Mineral. any of a complex group of hydrous silicate minerals, containing chiefly calcium, magnesium, sodium, iron, and aluminum, and including hornblende, tremolite, asbestos, etc., occurring as important constituents of many… …
128Pegmatite — is a very coarse grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic .Most pegmatites are composed of quartz, feldspar and mica; in essence a granite . Rarer intermediate and mafic pegmatite… …
