Since it is impermissible to eat clams, does that mean they are impure, just like impermissible animal meat?
In the Name of Allah, the Most Merciful and Compassionate
Even though clams are impermissible to eat in the Hanafi school, they are not impure. [‘Ayni, al-Binaya Sharh al-Hidaya]
This is because clams do not have flowing blood in them, similar to fish. [‘Ayni, al-Binaya Sharh al-Hidaya citing al-Sarakhsi]
For this reason, the slaughtering of an animal according to the conditions of Islamic slaughter removes the flowing blood from the meat, thus leaving it pure; whereas, fish are not slaughtered because they do not contain flowing blood that needs removing.
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani