Gabbro

Gabbro achieves a good toughness rating thanks to its compact, granular internal structure, which makes it resilient against breakage during daily use.

Gabbro is resistant to most daily use conditions such as water immersion, sunlight, dryness, and common stains. However, caution is advised with heat and harsh chemicals.

plagioclase, pigeonite, olivine, chromite , ilmenite

Gabbro is a strong and durable rock well-suited for construction, and it has been used as a paving stone, for curbing, and other outdoor construction uses. It can be crushed and used as an aggregate material for roads and ballasts for railroad tracks. Gabbro is also a common source of rare metals, including chromium and platinum.

Gabbro can be formed as a massive, uniform intrusion via in-situ crystallisation of pyroxene and plagioclase, or as part of a layered intrusion as a cumulate formed by settling of pyroxene and plagioclase. Cumulate gabbros are more properly termed pyroxene-plagioclase adcumulate. Gabbro is an essential part of the oceanic crust, and can be found in many ophiolite complexes as parts of zones III and IV (sheeted dyke zone to massive gabbro zone). Long belts of gabbroic intrusions are typically formed at proto-rift zones and around ancient rift zone margins, intruding into the rift flanks. Mantle plume hypotheses may rely on identifying mafic and ultramafic intrusions and coeval basalt volcanism. Nearly all gabbros are found in plutonic bodies, and the term (as the International Union of Geological Sciences recommends) is normally restricted just to plutonic rocks, although gabbro may be found as a coarse-grained interior facies of certain thick lavas.

Gabbro is dense, greenish or dark-colored and contains pyroxene, plagioclase, and minor amounts of amphibole and olivine. The pyroxene content is mostly clinopyroxene, generally augite, but small amounts of orthopyroxene may also be present. If the amount of orthopyroxene is more than 95% of the total pyroxene content (5% or less clinopyroxene content), then the rock is termed norite. On the other hand, gabbro has more than 95% of its pyroxenes in the form of the monoclinic clinopyroxene/s. Intermediate rocks are termed gabbro-norite. The calcium rich plagioclase feldspar (labradorite-bytownite) and pyroxene content vary between 10–90% in gabbro. If more than 90% plagioclase is present, then the rock is an anorthosite. If on the other hand, the rock contains more than 90% pyroxenes (often both are present), it is termed pyroxenite. Gabbro may also contain small amounts of olivine ("olivine gabbro" if substantial amount of olivine is present), amphibole and biotite. The quartz content in gabbro is less than 5% of total volume. 'Quartz gabbros' or monzogabbros are also known to occur, for example the cizlakite at Pohorje in northeastern Slovenia, and are probably derived from magma that was over-saturated with silica. Essexites represent gabbros whose parent magma was under-saturated with silica, resulting in the formation of the feldspathoid minerals nepheline, cancrinite, and sodalite as accessory minerals rather than quartz. (Silica saturation of a rock can be evaluated by normative mineralogy). Gabbros contain minor amounts, typically a few percent, of iron-titanium oxides such as magnetite, ilmenite, and ulvospinel. Gabbro is generally coarse grained, with crystals in the size range of 1 mm or larger. Finer grained equivalents of gabbro are called diabase (also known as dolerite), although the term microgabbro is often used when extra descriptiveness is desired. Gabbro may be extremely coarse grained to pegmatitic, and some pyroxene-plagioclase cumulates are essentially coarse grained gabbro, some may exhibit acicular crystal habits. Gabbro is usually equigranular in texture, although it may be porphyritic at times, especially when plagioclase oikocrysts have grown earlier than the groundmass minerals.

The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his description of these Italian ophiolitic rocks. He assigned the name "gabbro" to rocks that geologists nowadays would more strictly call "metagabbro" (metamorphosed gabbro).

Gabbro is said to be a spiritual stone that will help heal a person mentally and physically. Many psychics and shamans believe it can help reveal the darkness from past lives and deeds and allow the individual to move towards their higher purpose of living. For the most protective and cleansing energy, place these stones on your root chakra and crown chakra.