[Advaita-l] Singeri Acharyas Daily Puja

[Murali S]

I have a doubt.Its very 'mundane'' in the sense not very hi-fi shashtraaic.
In the recently concluded araadhana of Sri Abhinava Vidyathirtha
Mahasvaminaha(Mahaswamigal),Acharyal was doing abhishekham/puja to a
black salagraamam.

During Araadhana(i),is there any reason why saalagraramam is used?

Also in the daily Sri Chandramouliswara Puja at night,two salagramams
are used-one the above dark one and another of grey colour which I
believe is called Narasimha Salagramam.Why is it so called? And what
is the black salagramam called?

The sphatika lingam is enclosed in a murthi of Lord Iswara with Amba
mounted on Rishabha,I think.Where do the two salagramams go?

I hope the moderators do not mind this 'mundane' question.