I would be careful about paying for an app for this. Usually the app will require you to take a picture of the specimen and upload it for an ID.
The problem with rocks and minerals is that they have greatly overlapping colours, habits and morphologies and just identifying from photos is very difficult unless you happen on an almost textbook specimen.
To obtain a better ID, other factors that cannot be photographed such as SG, Hardness, Streak and even its geologic situation need to be considered.
It is great that you have an interest in mineral/rock identification and don’t want to dampen that, but as a first step I would recommend a good rocks and minerals book which usually also has a section detailing the use of other tests as mentioned to aid the ID. I have the following books which I find useful. The Pellant Smithsonian handbook is a particularly nice reference.