<Tr> <Th> Mohs scale hardness </Th> <Td> 2.5--3 </Td> </Tr> <Tr> <Th> Luster </Th> <Td> Silky </Td> </Tr> <Tr> <Th> Streak </Th> <Td> White </Td> </Tr> <Tr> <Th> Optical properties </Th> <Td> Biaxial </Td> </Tr>

Which of the following is not a type of asbestos