WorldWide Drilling Resource

Alaska Miners Association Phone: 907-563-9229 Fax: 907-563-9225 ama@alaskaminers.org www.alaskaminers.org American Exploration and Mining Assn. Phone: 509-624-1158 Fax: 509-623-1241 info@miningamerica.org www.miningamerica.org WorldWide Drilling Resource ® is proud to be a member of these mining associations. Women in Mining 866-537-9694 wim@womeninmining.org www.womeninmining.org 49 WorldWide Drilling Resource ® FEBRUARY 2015 Calcite and Dolomite by Harry W. Short Engineering Geologist Calcite is a common rock-forming mineral whose name was derived from the Latin word, calx, meaning burnt lime. Crystals of calcite are usually white or colorless, but impurities may tint it shades of gray, red, blue, green, or yel- low. Groundwaters carrying calcium car- bonate in solution precipitate calcite in a wide variety of environments. Calcite may be deposited as a coating along joint planes or fractures in sedimentary rocks; as a filling in rock cavities; as a cementing agent in sandstone and soil; and is common in limestone, marl, chalk, marble, and speleothems in underground caverns. Calcite crystals are generally well- developed and easily recognized, yet can appear in several complicated forms. The most common crystalline form of calcite is the rhombohedron with perfect cleav- age in three directions. Thus, the crystals will split or break parallel to the faces of the crystal, and each fragment will retain the rhombohedral shape. This feature can easily be observed by the eye in large crystals, and with a hand lens in small rock specimens. The rhombohe- dral crystal faces of calcite are perfectly formed, and those of dolomite are curved or warped. Dolomite often has a flesh- pink color due to the presence of mag- nesium. A chemical test for magnesium will separate dolomite from calcite and aragonite. Chemically, calcite (CaCO 3 ) is very similar to dolomite (CaMg)(CO 3 )2, and distinguishing between them can be diffi- cult. A simple test with hydrochloric acid (HCl) can be used. Place a drop or two of the acid on the sample, and carefully observe the reaction. Calcite will effer- vesce rapidly; and dolomite will not, un- less ground to a fine powder. Double refraction is an interesting feature that can be used to identify clear calcite crystals. Make a small ink dot on a piece of white paper. Place the crys- tal over it, observe the dot - two images will be seen. This occurs because light rays entering the crystal split into two rays, each having its own velocity and refractive index. Thus, the rays diverge, reach your eyes at a different velocity, and a double image is seen. Calcite is commonly used in building projects in cement and in commercial acid neutralization. Calcium carbonate is mixed with sugar and flavoring to make chewable tablets to neutralize stomach acids. It has also been spread on fields to reduce acid, and in rivers which have been turned acidic by min- ing or other reasons. Dolomite is crushed and sized for use as a road-base material, aggregate in concrete and asphalt, railroad ballast, riprap, or fill. It is also used in the pro- duction of cement and cut into blocks of specific size known as "dimension stone". Dolomite, like calcite, is used for acid neutralization in stream restora- tion projects and as a soil conditioner. It is a source of magnesia which is used as a feed additive for livestock, sinter- ing agent, flux in metal processing, and as an ingredient in the production of glass, bricks, and ceramics. Harry Harry Short may be contacted via e-mail at michele@ worldwidedrillingresource.com 4 *+ .* *..*( ,$''$)" **'- !--*,$!-5 111 %!).! # ,$''$)"-/++'3 *( !,0$)" .#! ($)$)" $) /-.,3 .#,*/"#*/. .#! 1!-. ((!,- $.- ,$'' .!!' / - ,$''$)" '/$ - #,! *(+*/) - !1 !,/) *. ,3 $.- $. $+! ) '$)" **'- )"!)/$.3 ,$0! + ,&- !0 #*)! !-. $) .,!!. '&* !0 2 Here are some unique uses for sodium bicarbon- ate, better known as bak- ing soda: Sweeter Tomatoes - Sprinkle baking soda near your tomato plants tomake your tomatoes sweeter. Pest Deterrent - Rabbits, ants, sil- verfish, and roaches do not like bak- ing soda and will stay away from it, so sprinkle some on the soil in your garden. Mix equal parts of baking soda and flour and dust broccoli, cabbage, and kale plants to kill cabbage worms. Weed Prevention - Pour baking soda into patio and walkway cracks to kill small weeds and prevent new ones from growing.