You can use a unglazed piece of porcelain tile for a 'streak plate' to check for streak. I've often used a piece of broken porcelain from an old kitchen sink. If you can sacrifice a piece of your find, wrap it in some old canvas and smash it up a bit with a hammer and then use a small shallow bowl as a mini-gold pan and swish it around to separate the mineral grains by specific gravity. Then try using your magnet and see what sticks and what doesn't. Use a piece of plastic wrap on the magnet to keep the grains from sticking to the magnet. Any metallic grains should flatten and bend like metal rather than shatter like most minerals do. If you have a hand lens or magnifying glass you can check the grains to see if they break along crystal planes or not as well as looking for such things as striations and fresh color. If you have one you can use a simple multi-meter in resistivity mode on one of your pieces or on a grain and see if it is conductive which will mean it is metallic Fe-Ni alloy.
I'd guess magnetite grains in those pieces. It could be pyrrhotite, an iron sulfide mineral that can be magnetic and you might smell sulfur if you heat some ground up material with a torch. The bottom pic with the shinny face is intriguing. There is a naturally occurring Fe-Ni alloy mineral called awaruite that occurs in peridotites and serpentinites but I don't know anything about the geology of Texas or if ophiolite complexes occur there which have those rock types but the Precambrian Texas Craton does outcrop in central Texas so who knows. A quick Google search shows some interesting geology there.
Awaruite also occurs in meteorites.
For future trips where one is looking down instead of up at the sky, for not too much money a person can purchase a small 16x hand lens, a set of hardness picks and a pencil magnet. As well a small steel or plastic gold pan is handy (especially if you're finding heavy minerals like magnetite in a stream bed). And a good rock and mineral field book is always money well spent. We amateur astronomers should always be ready to put on our amateur geology hat - just in case.
Neat find and good pictures to. Happy prospecting and keep us posted.