This work could not even have been attempted, much less completed, without the help of numerous friends and colleagues. In roughly chronological order (my sample collecting formally began in 1985), I extend my sincerest thanks to the following people, beginning with those based in Ohio institutions: N’omi Greber and David Brose, then at the Cleveland Museum of Natural History; Olaf Prufer and Mark Seeman at Kent State University;

Small children can distinguish different animal species from one another. Children encounter a wide range of plant and animal species in various ways: in illustrated books, in stories, in school, while drawing or engaged in handicrafts, and so on. From childhood on we are trained to distinguish plant and animal species from each other. But what is the situation with rocks and minerals? Rocks are simply “stones” or “rocks,” and “crystals” are understood to be simply well-formed and transparent rock crystals (quartz). We are not exposed to ways to engage with rocks to identify and classify them. That is certainly one initial disadvantage, even though children are usually fascinated by rocks. Place a small child on a gravel bank, and you will enjoy some quiet for quite a while. Geology is either not taught at all in schools, or taught very little. Since the subject matter is so complex, students (and frequently teachers) struggle to master the concepts. Even so, we are ready to face the world of rocks. <...>

The solid part of the Earth is made up of rocks. Rocks are made up of minerals. A mineral is a naturally
occurring inorganic solid. It has a specific chemical composition and a characteristic crystal structure.
Quartz is a very common mineral. Most beach sand is composed of quartz. It has the composition SiO2
and forms elongate 6-sided crystals that terminate at a point <...>

Uma das maiores dificuldades encontradas pelos autores no ensino de disciplinas relacionadas à Petro-logia ígnea e áreas afins nos níveis de Graduação e Pós-Graduação é representada pela falta de textos em português. Entre a tradução de um livro texto já existente e a preparação de um texto novo, os autores optaram, em 1979, pela segunda alternativa, uma vez que os textos já disponíveis se encontraram algo desatualizados e, muito raramente, tocam em assuntos de grande importância para o Geólogo brasileiro.

В данной книге изложены основы петрографии магматических горных пород.
В первой части дана общая характеристика магматических пород, рассмотрены форма и строение магматических тел, химический и минеральный состав, структуры и текстуры, образование и классификация магматических горных пород, их распространенность, ассоциации и причины разнообразия.
Во второй части приведено систематическое описание главнейших магматических горных пород и даны таблицы для определения их в шлифах

Austin F. Rogers, the senior author of the first two editions of this text and professor emeritus in mineralogy at Stanford University, passed away at Berkeley, California, in April, 1957. His wise counsel as a former professor and his judgment as a mineralogist have been greatly missed during this revision. On the other hand, many readers, particularly those most familiar with Professor Rogers and his work, will recognize the influence of his teaching and will remember portions of the text which remain unchanged in the third edition.

The ore microscope is the basic instrument for the petrographic examination of the large and economically important group of minerals referred to collectively as "ore" or "opaque" minerals. Although neither term is strictly correct (inasmuch as pyrite is opaque but rarely, if ever, constitutes an economically viable ore and sphalerite and cassiterite are important ore minerals but are not opaque), both terms are frequently used synonymously.

Literally, “Mineralogy” means science of minerals.

The term “mineral” was coined in the late Middle Ages; it is derived from the Medieval Latin word mina = shaft (minare = to mine). The antique people, e.g., the Greeks and Romans, only used the word “stone”. Special attention was dedicated to precious stones, distinguished by their lustre, colour and hardness, which were highly estimated by the old civilised nations already in pre-Greek times.