SOLVED. YA or juvenile fiction girl who travels to future by obelisk meets future twin [s]

[Lucy]

I read this book when I was about ten. It's about two girls, one in present, one in future. They both look alike and can travel to future or past using an obelisk that exists in both their times. Ring any bells?

[Deborah]

How far into the future? I read a book where it was (I believe a helmet) that allowed one of them to travel some years to the future; but only about one lifespan into the future. The other sister didn't travel back. The main character traveled to the not so distant future, met her sister who was the same age as the one who time traveled from the books "present day".

[Lucy]

Can't really remember - a few hundred years I think. long enough that they don't exist in each other's lifetimes, and the future is pretty futuristic. The obelisk was the main thing I remember!

[Deborah]

Not the same book then. Sorry!

[Lucy]

Thanks anyway! Just found out on Booksleuth it was We are Tam by Patricia Bernard. Appreciate your help though!

[Rainbowheart]

We Are Tam for the link.