My sister purchased this from a rock/fossil shop in Oregon. She was told it is a turtle coprolite from Madagascar. Though I am a VERY amateur rock and fossil collector, I questioned whether it is a coprolite. It is very heavy for its size and non-magnetic. After doing some research, I have come to the conclusion that it is Siderite from Salmon Creek, Washington, USA. I am doing a Rock and Mineral Show and Tell for my sister-in-law's 5th grade science class and want to make sure my identification is correct. Would anyone like to weigh in on this? I would appreciate feedback. Thank you.