The Four Twin Laws of Calcite and How To Recognize Them
作者:
R.Peter Richards,
期刊:
Rocks & Minerals
(Taylor Available online 1999)
卷期:
Volume 74,
issue 5
页码: 308-317
ISSN:0035-7529
年代: 1999
DOI:10.1080/00357529909602559
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Calcite collectors often ask, “How many kinds of calcite twins are there?” The answer is hard to give because the wordkindsis ambiguous. The question can be given an unambiguous answer, however, if the question is rephrased: “How many twin laws are there for calcite?” In this case, the answer is “four.” I will go further and assert that there are four, and only four, twin laws for calcite. The rest of this article will be spent explaining my answer and providing enough information that an observant collector should be able to tell whether a calcite crystal is twinned or not and to determine which of the four twin laws is represented. The basics of calcite crystallography are well covered in the excellent article by Brock (1993), and basic aspects of twinning are covered by Werner Lieber elsewhere in this issue.
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