Yes. All bullion in storage are fully insured.
Related articles:
Where are my bullion physically stored?
http://help.stackermarket.com/en/articles/5355736-where-are-my-bullion-physically-stored
What is the fee for storage per year?
http://help.stackermarket.com/en/articles/5355737-what-is-the-fee-for-storage-per-year
Can I visit my bullion and withdraw in person?
http://help.stackermarket.com/en/articles/5355747-can-i-visit-my-bullion-and-withdraw-in-person
Is there proof my bullion is physically held in a vault?