Tektites range in size from microscopic grain to masses weighing tens of kilograms. Most tektites are brown in transmitted light and appear black in reflected light. Some are olive brown and others are in various shades of green. They are generally spherical in form, but they also come in various shapes from flat to round, oval, teardrop, and dumbbell form representing different state of viscosity. These are naturally occurring glasses of possible extra terrestrial or impact origin.
Philippine tektites are called rizalites. Locally it is called “Tae ng Bituin”. They also come in various shapes and sizes. Variety of surface texture like wrinkles, grooves, pits and vesicles are common.
The average age of Philippine Tektites correlates with other tektite dates from Australian strewn tektite field which average about 710,000 year old. Australian Strewn Field covers from Australia to the Philippines, South-east Asia, China and West of Madagascar.
Tektites can be found along plains all over the country. Places, which yield huge number of these black glassy objects, are Cagayan Valley, Pangasinan, Rizal, Bicol, Iloilo and Agusan.
During Prehistoric times, early man used these objects as charm-stone or amulets while others used this as tools and ornaments. In 1926 Bayer encountered this black object in a prehistoric age site dating around 200 BC. In Cagayan Valley, these were found in Pleistocene sediments containing fossils of elephants and rhinoceros and stone tools.