Mineral group also called "nesosilicate," containing isolated SiO4 tetrahedra that are bound by interstitial cations. Their structures are usually closely packed resulting in high density and hardness, with fairly uniform properties in all crystallographic directions. Substitution of Al3+ for Si4+ is generally low. The most common othosilicate is olivine, which Inorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous, Zr(SiO4), observed in all terrestrial rocks type and in ordinary Chondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such, Most common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after, mesosiderites, and lunar rocks.