Table of Contents
What minerals have a white streak?
| Streak Colors of Common Minerals | |
|---|---|
| Andalusite | White or colorless (hardness is about the same as the streak plate). |
| Titanite | White. |
| Topaz | Colorless (harder than the streak plate). |
| Tourmaline | Colorless (harder than the streak plate). Specimens often fracture, shedding small particles. |
What mineral does not have cleavage?
Quartz has no mineral cleavage and fractures the same irregular way glass breaks.
What mineral is white and feels greasy?
| MINERAL NAME | LUSTER (appearance) | DISTINGUISHING PROPERTIES |
|---|---|---|
| Halite | Non-metallic | 3 perfect cleavages at 90°; Tastes like salt, feels greasy. |
| Gypsum | Non-metallic | Generally clear to white; One perfect cleavage, may show up to 3 cleavages; Easily scratched with a fingernail. |
Which of these minerals is known for a luster that is greasy?
Specimens with a greasy luster appear to be coated with a thin layer of oil or grease. Some specimens of serpentine, jade, diamond, vesuvianite, and nepheline have a greasy luster.
What is luster and streak of mineral?
Lesson Summary. Minerals have distinctive properties that can be used to help identify them. Color and luster describe the mineral’s outer appearance. Streak is the color of the powder. Mohs Hardness Scale is used to compare the hardness of minerals.
Does fluorite have metallic luster?
Metallic luster – brownish cubic crystals of galena. Non-metallic luster – purple cubic crystals of fluorite.
What mineral has a greasy feel?
Talc
Talc is the softest mineral, demonstrated by its position at the bottom of Mohs’ Scale of Hardness with a relative hardness value of 1. It has a soapy, greasy feel.
Which mineral has a greasy feel and a black streak?
| Hardness | Color | Notes |
|---|---|---|
| 1+ | Dark-red to Vermilion | Exhibits a wide range of hardness depending on form; crystalline hematite is harder. |
| 1 to 1½ | Steel-grey to Iron-black | Has a greasy feel. |
| 1 to 1½ | Bluish-black | Has a greasy feel; heavier than graphite |
| Hardness | Color | Notes |
What is a pearly mineral?
Pearly – Describes a luster similar to the inside of a mollusk shell or shirt button. Many micas have a pearly luster, and some minerals with a pearly luster have an iridescent hue. Some minerals may exhibit a pearly luster on cleaved crystal surfaces parallel and below the reflecting surface of a mineral.
What kind of minerals are gray in color?
Sodium-rich varieties are white or light gray; calcium-rich varieties are medium to dark gray. Labradorite variety shows blue play of colors. Most commonly found in granites and pegmatites. Often in barrel-shaped crystals.
What is the hardness of a luster mineral?
Luster nonmetallic. Color varies but dark red and reddish brown most common. Hardness 6.5-7.5.
What do biotite and muscovite minerals look like?
1 Biotite and muscovite belong to a family of platy minerals called “mica”. All have one strong cleavage and form sheets that you can pick apart with a knife or your fingernail. Micas strongly reflect light and appear shiny. Muscovite is also called “white mica” and biotite is sometimes called “brown mica” or “black mica”.
What kind of minerals are found in igneous rocks?
Minerals (Na, Ca, Mg, Fe, Al Silicates) Luster nonmetallic. Color dark green to black. Hardness 6. Cleavage 2 directions at nearly 90º (pyroxene) and 2 directions at 60º and 120º (amphibole). Dark-colored igneous rocks and gneiss. Some amphibole minerals formerly used as asbestos; some pyroxene minerals used as source of lithium.