A class of stony meteorite usually (though not always) lacking the tiny, rounded inclusions known as chondrules found in chondrites. Achondrites make up about 9% of all meteorite falls. They consist principally of one or more of the minerals plagioclase, pyroxene, and olivine. The main distinction between achondrites and chondrites is that the achondrites have different abundances of calcium and similar elements, and almost no metal or sulphide. Achondrites are thought to have crystallized from a magma in the same way as terrestrial rocks. The achondrites are divided into five main classes. The two main calcium-rich classes (containing more than 5% calcium) are the pigeonite–plagioclase achondrites (eucrites) and the plagioclase–hypersthene achondrites (howardites). There are three main calcium-poor classes (usually less than 1% calcium): the hypersthene achondrites (diogenites), the olivine–pigeonite achondrites (ureilites), and the enstatite achondrites (aubrites). The eucrites, howardites, and diogenites are often collectively referred to as the basaltic achondrites. The pigeonite–maskelynite achondrites (shergottites), augite–olivine achondrites (nakhlites), and olivine achondrites (chassignites) comprise the rare SNC meteorites, which are thought to come from Mars. There is also a very rare class of augite achondrite, the angrites, named after the Angra dos Reis meteorite, which fell in Brazil in 1869.