Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix.

Peridotite is a generic name used for coarse-grained, dark-colored, ultramafic igneous rocks. Peridotites usually contain olivine as their primary mineral, frequently with other mafic minerals such as pyroxenes and amphiboles.

2023年7月12日 · Peridotites are dense, coarse-grained, dark-colored ultramaficplutonic rocks with at least 40% olivine by volume. Members are dunite, kimberlite, harzburgite, wehrlite and …

2022年9月2日 · Porphyritic texture describes an igneous rock texture with large crystals embedded in a finer-grained matrix. It can occur in virtually all igneous rocks, i.e., intrusive and …

FRAGMENTAL TABLE 4-1. USAGE OF THE WORDS PORPHYRITIC AND PORPHYRY FOR AN IGNEOUS ROCK CONTAINING POTASH % Phenocrysts FELDSPAR AND QUARTZ Groundmass

The rock is a porphyritic peridotite with abundant phenocrysts of olivine, in places altered to serpentine. Garnet (pyrope) and ilmenite are common, along with some plates of biotite, enstatite, and apatite.

In general, scoria is basic; basic obsidian is called "tachylite"; and spherulitic tachylite is "variolite." Normally it is not possible to determine the composition of these rocks. They are customarily …

2023年1月5日 · Peridotite consists in part of the minerals olivine and pyroxene. The Elliott County peridotite is a special type of peridotite called kimberlite. It is dark green to black and composed of various grain sizes (porphyritic texture) in a fine- to medium-grained groundmass called a matrix.

Porphyritic rocks are those that contain large crystals (phenocrysts) embedded in a fine-grained matrix. Peridotite is aphanitic, meaning it has a fine-grained texture without any crystals.

Kimberlite is defined as a porphyritic alkali peridotite containing abundant phenocrysts of Olivine and phlogopite in a fine-grained groundmass of calcite and second generation olivine and phlogopite, and with accessory ilmenite, serpentine, chlorite, magnetite, and perovskite.