Gabbroiseen

Gabbroiseen is the illative singular form of the Finnish adjective gabbroinen, meaning gabbroic or related to gabbro. In Finnish geological writing, adjectives are inflected for case, so gabbroiseen is used when describing something that relates to gabbro in contexts expressing movement toward or inclusion in that rock type.

Gabbro is a dark, coarse‑grained igneous rock that crystallizes from mafic magma at depth. It is the intrusive counterpart to basalt and is typically composed mainly of plagioclase feldspar and pyroxene, with smaller amounts of olivine, amphibole, or biotite. The crystals are large enough to be seen without a microscope, giving gabbro its characteristic texture.

Mineral assemblages in gabbro are generally dominated by plagioclase feldspar and pyroxene, with accessory minerals. The texture and mineralogy distinguish it from finer-grained basalts and from more felsic intrusive rocks. In classification schemes, rocks with a similar mineral balance but coarse grains are termed gabbro, while basalt refers to the fine‑grained, volcanic equivalent.

Formation and occurrence: gabbro forms when mafic magmas cool slowly within the crust, allowing large crystals to grow. It commonly occurs in large plutons and dikes, and is a major component of layered intrusions and the lower oceanic crust in ophiolite complexes. Gabbroic rocks provide important records of crustal crystallization and magmatic differentiation.

Uses and significance: due to its durability and strength, gabbro is used as dimension stone and aggregate in construction. Geologically, gabbro helps researchers understand crustal growth, plate tectonics, and the magmatic processes that differentiate mafic rocks from basalt.