Altars; the spiritual table of transcendance

[Ashim]

If all of my crystals lie on a furniture that has other purposes elsewhere than that surface, does that count as an altar?

No, an altar should be a dedicated place of focussed attention.

The surface where the crystals have been placed did have focused attention though.

The entire area should be pure. Any distortion will be magnified. Set aside a space, pure, undistorted for your magical workings.