Not only will a T1 or T2 Veldspar mining crystal work with Veldspar, Concentrated Veldspar and Dense Veldspar. It will also work with Banidine, a useless variant of Veldspar found in some missions.

The same is true for all the other mining crystals. That is, they work for all the variants of the type of ore they are made for.

To add to these answers which are nice and correct it is worth pointing out that a T2 strip without a mining crystal loaded yields less ore than a T1 strip.

So only use T2 strips if you are going to be using crystals.

It is also worth adding that the crystals are definitely worth it, especially the T2 variants. Their cost is easily outweighed by the boost in yield they provide.

Yes they do. Even the Tech 2 ones.

if you have a veldspar crystal either t1 or t2 it gives the bonus only when you mine all kinds of veldspar. if you warna mine somethign else change crystal.

Check the stats of the Mining Laser you are using, you'll see two mining amount values. You'll only extract at the "specialty" rate if you're using a Crystal and the relevant roid. For example, a T1 or T2 Veldspar Mining Crystal whilst mining any variant of Vedlspar.

If you used a T1 or T2 Veldspar Mining Crystal whilst mining anything else then you'll extract at the mining amount value (which will be lower).