There are several tests that can be used to try and identify
those rocks you are not sure what they are.
The Scratch Test, to check for the Hardness of the material.
The Streak Test, to see what color the specimen in question
leaves on a clean white piece of unglazed porcelain.
Fluorescence, can be a telling test, especially on specimens
that you are unable to perform either of the above tests on.
And Specific Gravity, which is finding what the "density" of
your specimen is.
All minerals have a calculated designated Relative Density.
This Relative Density (RD), in the past has been called the
Specific Gravity (SG) of a material. Today RD is the preferred
term, but either is still accepted.

Finding the SG/RD of a material is probably the hardest of
all the tests to perform since you have to make a device
to test for it. It is not Rocket Science however and anyone
with access to the needed parts should be able to manage.

Here is a picture of such a home-made device I borrowed
from a member of our local rock club.
It has a small scale as the platform with a small plastic cup
attached and suspended below the platform. The bottom
portion of the plastic milk container to the right is filled with
water and the small plastic cup is submerged so that is not
touching either the sides or bottom.

So here are our test results.
I will list the correct designated SG/RD for each mineral
after the heading.

Quartz-  SG/RD,  2.65
Quartz Crystal;
Dry7.44 - Wet4.64 = 2.80.  7.44/2.80 = 2.65
Polished Quartz;
Dry5.32 - Wet3.31 = 2.01.  5.32/2.01 = 2.646

Topaz-  SG/RD,  3.4 - 3.6
Dry8.24 - Wet5.90 = 2.34.  8.24/2.34 = 3.521

Pyrite-  SG/RD  4.9 - 5.2, average 5.0
Dry17.84 - Wet14.12 = 3.72.  17.84/3.72 = 4.795

In this test our results for the Pyrite is the only one that
falls considerably outside the designated range. This makes
me want to look up the SG/RD for other possibilities such as
Marcasite or Chalcopyrite.

And one final test.
Pictured below is a cabochon I made out of some of our
local pink Feldspar. There are many types of Feldspar and
I have assumed this would be an Orthoclase.
First I looked up the designated SG/RD for a few types
of Feldspar.

Anaclime-  SG/RD 2.2 - 2.3
Orthoclase-  SG/RD 2.5 - 2.6
Plagioclase-  SG/RD 2.62 - 2.76

Test results on the cabochon;
Dry5.27 - Wet3.20 = 2.07.  5.27/2.07 = 2.5458

Which places it firmly within the range of Orthoclase.