Hi Nishedha, I took some of my turquoise out and hot pin tested it..maybe a scratch but no indentations and no chemical smells. Like I said, the turquoise with the dark (iron pyrite or iron oxide/hematite) matrix will show some subtle organic interplay between the turquoise and the dark matrix: fuzzy edges for lack of a better description. Look at several beads, and inside the hole with a loupe too to check color changes- some are very chalky & much lighter inside- not a great sign. They do treat surfaces with wax and some polymer, which is OK, depending on the price and can add to durability.
Sometimes you'll see a gradual rust staining into the turquoise ( first and second photos), sometimes a flower pattern of the turquoise (like in the third and last photo). Sometimes spiderweb pattern like the donut. Or just random like the next donut, more matrix but "natural" turquoise patterns.

Also check for cracks and defects in turquoise with your loupe. I wish I had round beads to show you as they can look quite different. But the general ideas are the same. As far as color, go by what you like. Some of my best turquoise looks "fake" because the color is so pretty. Usually the bead color will vary some or have subtle differences- but not always. The color will change over time too, as worn and mixed with skin oils, especially if natural.

The colors you picked are really pretty, and look natural- in fact yours would be a nice match with many expensive pendants and other beads. While always good to be skeptical- especially if expensive...generally go by what you like is the best advice I've read in this Forum.

MOHS Hardness of Iron Pyrite is 6-6.5
MOHS Hardness of Iron Oxide-Hematite is 5.5-6.5
MOHS Hardness of turquoise is 5-6. The finest is said to reach hardness of 6
MOHS Hardness of Howlite is 3.5
MOHS Hardness of Magnesite is 3.5-4.5/5

Examples: Vintage Chinese "Tibetan" Turquoise most from from Hubei mine, China, now closed.
EDIT: There is also turquoise from the American Southwest that has a dark iron based matrix (Lander Blue, Bisbee, #8, Morenci, and Red Mountain mines to name a few. The best turquoise from both China and the USA can be sometimes difficult to distinguish, and both are expensive these days. Good, hard, and well colored Chinese (and other) turquoise has gained respect and has been utilized in Native American Jewelry for many years now, especially the spiderweb and other matrix patterns that resemble the more expensive and difficult to find similar looking turquoise from the Southwestern USA and also Mexico. I am only showing dark matrix here.