SOLVED. YA Fantasy, Time Travel: Unhappy Girl whisked back in time to live with Neanderthals. [s]

[Sforster]

An unhappy adolescent girl who lives in a present day city, (I read it in the late 1970's) becomes upset and runs to a nearby park to hide by her favorite boulder. Somehow she is transported back in time to live with a tribe of cave people/neanderthals. She has trouble adjusting at first, but learns their language and finds acceptance in the group. She has some things in her pocket including a pocket knife and a safety pin, which she treasures as links to her past/the future. The value that she places on these items eventually causes problems and when she becomes very upset she is again transport through time, to her own time. She has mirror opposite problems re-adjusting to modern life. The book ends with her menstruation cycle starting for the first time.

[Louie]

This sounds similar to Saturday, the Twelfth of October by Norma Fox Mazer. It was published in 1975.

[Sforster]

Louie wrote: "This sounds similar to Saturday, the Twelfth of October by Norma Fox Mazer. It was published in 1975.

"

You are right, that DOES sound like that book. Even the title sounds familiar! This might be it.
Thanks.

[Rainbowheart]

Do you want us to move this over to Solved?

I'm 100% sure this is your book. The MC's first period is a pivotal point in the story just like you described.

[Kris]

Here is Amazon's "Look Inside" preview of Saturday, the Twelfth of October by Norma Fox Mazer - Louie's suggestion:

https://www.amazon.com/Saturday-Twelf... There are different cover images.

Excerpt: "Maybe that was why she especially loved the old boulder in Mechanix Park. Nothing, she was sure, would ever change that rock... Blistered and bumpy, criss-crossed with crevices and cracks, at least six feet high and twice as wide, the boulder heaved blindly out of the earth."

[Sforster]

Yes You are correct.

[Kris]

Glad you found your book, Sforster. Thanks for the update.