A. Can be scratched by a fingernail Chalk Dilute hydrochloric acid fizzes on it Clay Earthy odor when breathed on Diatomite Crumbly Rock gypsum Made up of the mineral gypsum Soapstone Soapy or greasy feel B. Cannot be scratched by a fingernail but can be scratched by ordinary pocket knife Dolomite Dilute hydrochloric acid may fizz slightly on it; will fizz if rock is powdered Limestone Dilute hydrochloric acid fizzes on it Serpentine rock Commonly some shade of green Shale Breaks in flat, thin flakes; earthy odor C. Cannot be scratched by an ordinary pocket knife Basalt Dark colored and heavy Chert Hard, smooth, and porcelain-like Rhyolite Light to dark colored; may show streaks or flow structure 3. GRANULAR appearance (at least some of the individual grains are large enough to be seen without a magnifying glass) A. Can be scratched by an ordinary pocket knife Limestone Dilute hydrochloric acid will fizz on it Marble Dilute hydrochloric acid will fizz on calcite marble, and it may fizz slightly on dolomite marble Rock gypsum Made up of the mineral gypsum Rock salt Has a salty taste; made up of the mineral _halite_ B. Generally cannot be scratched by an ordinary pocket knife (some schist is softer) Grains are of about equal size (equigranular) 1. Granite Quartz and feldspar grains interlock Pegmatite Large interlocking grains; commonly feldspar, quartz, mica Quartzite Rock breaks across the quartz grains Sandstone Rock breaks through the cement but around the sand grains Easily seen grains are scattered through a mass of finer grains 2. Basalt Dark colored, heavy rock Llanite Rusty pink feldspar and blue quartz grains embedded in a brownish rock mass Rhyolite porphyry Light to dark colored rock; may show streaks or flow structure Grains are arranged in layers 3.