Here is a geology text that assumes no conflict between Christianity and science and is faithful to Church teaching. This book covers basic topics in geology, including the Earth's age and composition, the dynamics of continental plate motion, classification of rocks and soil, effects of glaciers, radiometric dating, and more. The illustrations are lovely and hand-drawn – not what you would expect in a textbook. However, I prefer a few glossy photographs as well, but you can find these on the internet. I was unfamiliar with many of the geologic terms so I learned a lot along side my 12-year-old daughter. I especially appreciated the author's explanation of evolution in the appendix and Chapter 11 on the geologic column in the Williston Basin.

I allotted 18 weeks to finish this book, but it took 22 weeks, rushing a bit. The book has suggested research activities at the end of most chapters, but we did not do very many of them. (I had already ”planned” one semester of chemistry to follow one semester of geology.) The last chapter consists of short biographies of mostly Catholic scientists. There is also a suggested reading list at the end of the book. Exercises are included at the end of each chapter - lots of crosswords, matching, fill-in-the-blank, multiple choice, etc. There are also poems interspersed throughout the text to aid in memorization. If we had done more research activities and added supplemental reading, this book would expanded into a full-year course. There were no tests included so it was necessary to make some to reinforce the material.

Mary Daly mostly separates scientific considerations from philosophical ones. She sticks her opinions in the appendices. However, the one exception is in the first chapter when she explains charitably that Young Earth Creationism is inconsistent with scientific evidence.

Here are some of the ideas (as far as I can understand) that really distinguish this book from most geology texts aimed at the home school market:

• The text is consistent with our Catholic Faith.
• Radiometric dating of rocks shows that the Earth is about 4.5 billion years old.
• While we are all descended from two first parents, the fossil record points to a single "family tree of life" of which we are a part.
• Evolution of new species by natural selection is an incomplete explanation of the fossil record. In an appendix, the author suggests that additional mechanism is needed to account for the sudden appearance of new species in the fossil record. John Davison, a professor of zoology, developed a semi-meiotic hypothesis as just this sort of mechanism. I found this very intriguing since it is compatible with what is observed and is testable. Mary Daly also suggests that some paleontologists have a philosophical bias that prevents them from considering other scientific explanations.
• The geologic record does not support a worldwide flood. Mary Daly explains there is not enough water on Earth to do this. She suggests that Noah's flood was probably a catastrophic flood that affected the part of the world known to the inspired writer.

Overall, I think A Doorway of Amethyst is a very good, well-written geology text. I am grateful that Mary Daly took the time to write it. I recommend it and plan to use it again. Next time, I would want to write cumulative quizzes for each chapter, allow more time for supplemental reading, and incorporate more projects and writing assignments. (I can dream, anyway.)

You can view sample pages at the end of this document on the author's Hedge School website.