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Peridot olivine is the birthstone for the month of August. [17] Peridot has often been mistaken for emerald beryl and other green gems. [18] Noted gemologist G.F. Kunz discussed the confusion between beryl and peridot in many church treasures, most notably the "Three Magi treasure" in the Dom of Cologne, Germany. [19] [1]
The word peridotite comes from the gemstone peridot, which consists of pale green olivine. [1] Classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green. Peridotitic outcrops typically range from earthy bright yellow to dark green; this is because olivine is easily weathered to iddingsite ...
Olivine has many uses, such as the gemstone peridot (or chrysolite), as well as industrial applications like metalworking processes. Olivine in cross-polarized light. The ratio of magnesium to iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember: Mg 2 Si O 4) and fayalite (Fe-endmember: Fe 2 Si O 4).
Dunite may also form by the accumulation of olivine crystals on the floor of large basaltic or picritic magma chambers. These " cumulate " dunites typically occur in thick layers in layered intrusions , associated with cumulate layers of wehrlite , olivine pyroxenite , harzburgite , and even chromitite (a cumulate rock consisting largely of ...
It consists of centimetre-sized olivine crystals of peridot quality in an iron-nickel matrix. Coarser metal areas develop Widmanstätten patterns upon etching. Minor constituents are schreibersite , troilite , chromite, pyroxenes, and phosphates ( whitlockite , stanfieldite, farringtonite, and merrillite ).
Peridotite, a type of ultramafic rock. Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals (dark colored, high magnesium and iron content).
Olivine lamproites are ultrapotassic, peralkaline rocks rich in volatiles (dominantly H 2 O). The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to "tetraferriphlogopite" (anomalously Al-poor phlogopite requiring Fe to enter ...
Orange forsterite with a portion of tephroite. Pure forsterite is composed of magnesium, oxygen and silicon. The chemical formula is Mg 2 SiO 4.Forsterite, fayalite (Fe 2 SiO 4) and tephroite (Mn 2 SiO 4) are the end-members of the olivine solid solution series; other elements such as Ni and Ca substitute for Fe and Mg in olivine, but only in minor proportions in natural occurrences.