1) What makes marble and granite different?
Marble is crystal grained metamorphosed carbonaceous rock. It is mostly chalk-stone (chalk) and it is more rarely dolomite. However, many other rocks are referred as marble in the building stone industry. The color of marble is bright but marble can be multicoloured when it contains tiny part of additives, i.e. silicates, iron oxides and blacklead. It can be yellow, brown, red, green and even black then. Marble is mostly fine-grain but some varieties of marble are made up of large crystals. Usually chalky (calcitic) marble dissolves in the diluted acids (salt, sulphur and nitrogen) but dolomite marble dissolves in acids only if they are poundery. Clean chalky (calcitic) marble is good insulator of the electric current.
Granite is most widely spread mountain rock on the continental surface of the earth. It is clear crystal hard-grain, averaged-grain and fine-grain rock that has formed while the magmatic lava freezes deep in the earth. Granite can be formed in the metamorphic process. Sometimes granite has both magmatic and metamorphic origin. The color of granite depends on the mineral structure of granite. The dominated minerals in granite are feldspar, blacklead and quartzite. Feldspar and blacklead provide granite dark color, and quartzite, which is usually hard-grain, is colorless or clear. The main difference between marble and granite is origin: marble is aqueous rock and granite is magmatic rock.
2) Why do the letters graven in granite lose their clearness after being moistened?
Granite is made up of minerals, and minerals consist of even tinier microminerals. When granite gets moisture, water fulfils all the gaps among minerals and microminerals. Light falls on the wet granite and a part of the rays breaks and disperses when they reach the surface of water. Therefore incomplete number of the rays reflects and reaches our eyes because a part of the rays has changed the direction. In other words, since the smaller amount of light comes from wet surface (part of the rays dispersed, broke and changed the direction) that area seems darker than dry granite around that area. Little by little water vapours and more and more the reflected light reaches our eyes and, therefore, we see clearer again.
3) What can be used to polish the surface?
It is recommended to clean the polished surface of granite with acid-free cleansers. If the letters graven in the tombstone monument 'overgrew' with impurities, you can clean them with a hard brush (non-metal) and solution of laundry soup and water. Unpolished (bushhammered, cutted, dressed) surfaces of granite are cleaned in the same way.
4) How to keep up humidity in the grave place?
The most widely used soil in the cemetery is sand and gravel, which easily leak. Therefore many people face the problem of watering. It is particularly a problem when it is intended to seed the lawn. It is recommended to dig out about 30 to 40 cm of soil from the grave place and drop off some clay, which should be properly rammed down, and cover the grave place with 10 cm of it. Then it is necessary to drop off some black earth (the layer of 20 to 30 cm). Clay will not let water in sand and gravel and humidity will last for a longer time.
5) The burial order in Vilnius city.