The book "Oligoclase" offers a comprehensive introduction to the mineral oligoclase, which belongs to the plagioclase feldspar group. It covers the chemical composition, crystallographic properties, and physical characteristics of this important rock-forming mineral. Oligoclase is a high-sodium feldspar that crystallizes in the triclinic system and has a Mohs hardness of 6 to 6.5. The specific gravity ranges from 2.64 to 2.66. The book draws on articles from Wikipedia and other free sources to provide a well-informed and accessible presentation of the topic. It is suitable for both professionals and enthusiasts who wish to learn more about the properties and significance of oligoclase.