SOLVED. Girl on an island with her brother and a mysterious cat, mystery/adventure children's book [s]

[Tonia]

SOLVED. Genre: children's chapter book, Mystery/Adventure for young children up to 12 years old. I read this book sometime in the mid 1990s but I can't remember which year I read it specifically. I would guess that the book was published somewhere between the 1980s to early or mid 1990s.
A school-age girl goes to live on an island with her brother for summer vacation. They meet a mysterious cat and the girl talks into a recorder, describing her adventures to her teacher and classmates. At one point in the story, her brother who is fascinated by the rocks on the island, picks up a rock and licks it, saying something like: "this rock tastes old." I don't remember if the island was tropical or not.

[Tonia]

My sister found the book for me and this post is hereby SOLVED. The book is called "The Broccoli Tapes".

[Rainbowheart]

Glad you found it!

The Broccoli Tapes for the link.