I'm going on the crystal "forms" developed (pattern of faces) - photos not good enough to be sure, but looks like dogtooth spar (calcite) not quartz to me. AtomRat is right - vinegar will only fizz slowly and can be washed off quickly without a huge hole being left. You mention matrix so maybe that has a bit of stuff in it to test that is not as nice as this crystal. In which case scratch it as well - calcite is hardness 3 and even a nickel coin will scratch it - a pocket knife blade can dig trenches in it.
Learn the Moh's hardness scale and carry a bit of quartz (7) miniature steel pocket knife (5-6), dollar coin (4) to test with. A "streak plate" (rough, broken face of white porcelain), pen manget and 10x and 20x hand lenses are useful, and I carry a 50% HCl mixture in a special bottle that I have in a pouch on my belt together with my pick (the knife, two lenses and mini-pen magnet hang on a leather thong around my neck - the mini-magnet is 3 cm long cut from a longer pen magnet, which I find tends to be a nuisance in my pocket. With the magnet, you dangle it on the thong next to the specimen and see if it deflects towards it - detects even minor magnetism.
http://www.prospectors.com.au/p-27-45ml-acid-dropper-bottle.aspx
http://www.prospectors.com.au/p-2397-proearth-leather-acid-dropper-case.aspx
http://www.prospectors.com.au/p-2577-geological-swing-pivot-magnet.aspx
http://www.prospectors.com.au/p-2390-estwing-no-3-sheath-for-pointed-pick.aspx
http://www.prospectors.com.au/p-2391-estwing-no-4-sheath-for-chisel-pick.aspx
if you do this sort of thing all day long you fork out for convenience
For those who drive a Mercedes 4x4 and who have everything:
http://www.prospectors.com.au/p-51-moh-scale-hardness-points.aspx
Field bags are the biggest thing for geos - there are plenty of cheap ones but take advice from a dinosaur, this is definitely the best:
http://geology.com/store/rock-bag/rock-bag.shtml
Not for the reasons you might think - strong, many good compartments, water-bottle container. The reason is climbing on cliff faces etc and coolness - limited contact with your body (sweating in hot weather), a loop for your geo pick so you don't have the restriction of it on your belt but still within easy reach, and a good second strap that stops it swinging out from your body - the number of times a bag full of rocks nearly pulled me off a rock ledge into oblivion! The water bottle is also than external special pouch and in easy reach. Prices for this vary around 400% - I got mine from a Nevada dealer including freight from the USA in only a few days for less than half what a Perth dealer wanted without freight included.
Moh's scale:
1=T= talc
2=G= gypsum
3=C= calcite
4=F= fluorite
5=A= apatite
6=O= orthoclase
7=Q= quartz
8=T= topaz
9=C= calcite
10=D=diamond
T = the
G = girls
C = can
F = flirt
A = and
O = other
Q = queer
T = things
C = can
D = do
(i'm a polite lad)
